Yeah! I have a few questions, though.
Are alternate builds required (as they play such a major part in the game)?
If we include bases (Masman8675 created some custom toy tags that are impossible in build but accurate in shape) what color should we use? Trans-orange (for Y2) or what we think Y3 will be (perhaps trans-green or trans-red or trans-purple or trans-black)?
What is the tag used to enter?
And finally, is it limited to one creation per user? Or are multiples valid?
Thanks in advance! 😛

So wow, I forgot a lot (or wasn't clear enough). If you include bases, the color is up to you, but you will need to subtract the amount of parts from your total (Just put it in the description). Alt builds are required, and that kinda brings me to another point; I would recommend that you add what powers/alt skins/etc the characters/vehicles would have in the description. The tag will be "Dimensions Contest". You can have multiple entries into each group, but I wouldn't recommend doing a ton of each. Good luck!

Looks good! Here are the bases I made: http://mecabricks.com/en/models/qxov7zEwj0D and http://mecabricks.com/en/models/kLyjWPYAvJr The only problem I have with the rules are the powers. I've never played the game, (even though I have two Dimensions sets) so I don't know much as to how they apply.

It's not super important, but it's things like flight, lasers, missiles, magic, etc. If you've played any other Lego games, that should help as well. The Lego Dimensions Wikia (http://lego-dimensions.wikia.com/wiki/List_of_Abilities) can be of use as well.

I have the game and have played it quite a bit so I can give a reasonably exhaustive list here, for those who don't feel like going to the wikia 😛
The most common (or default) vehicular Dimensions abilities include:
Accelerator Pads
"Treadmills"
Driving
Flight Docks
Cargo Hooks
Flight
Attacks
Underwater (swimming)

Some of the rarer abilities are:
Silver Blowup
Gold Blowup
Sonar Smash
Guardian Ability
TARDIS Time Travel (Rare)
Delorean Time Travel (rare)
Companion Cube Buttons (rare)
Sentry Turret Switches (rare)
BMO Game Docks
Midway Arcade Docks (rare)
Underwater Drone (somewhat rare)
Turning Gizmo into a Gremlin (limited to the Scooby-Snack)
Water Spray (somewhat rare)
Cracked LEGO Walls (pretty rare)
Ghost Trapping (rare)
Ghost Suspension (even rarer)
Targeting
...and probably some more that either I don't know of or that have not been released yet. 😛

Character Abilities so far include:
Magic
Targeting
Portal Creation (Chell)
Alternate Portal Creation (Raven)
Batarang Switches
Agility
Flight
Swimming
Super Strength
Gold LEGO Blowup
Silver LEGO Blowup
Intelligence
Hacking
Relic Detection
Grapple Points
Drone Access
Mini Access
Dectective Mode (TBA)
Lantern Construct Zones
Ghostbusting
Charge Transfer
Lock Picking (Fantastic Beasts)
Suitcase Access (Fantastic Beasts)
Vine Cut
Ghost Immunity (Slimer)
Big Transform
Slurp Access
Red Demon Objects (Adventure Time)
Sword Switches (Adventure Time)
Parseltongue
CHI Up
Spinjitzu Switches
Electrical Switches
Fuse Boxes (Mission:Impossible)
Master Build
A-Team Master Build
Broken Items Repairing
And a whole bunch more. 😛

Included Keystones Are:
Shift (basically portal access)
Chroma (Painting the Toy Pad)
Elemental (Fire, Water, Earth, and Lightning)
Scale (BIG or small)
Locate (random object detection)
RIP (alternate universe access) (Ghostbusters)
Create (animal creation) (Fantastic Beasts
TBA TLBM Keystone

And an additional couple of questions: are "custom" abilities/keystones fine? And when is the deadline? Thanks!

Custom abilities are fine, just try not to go too crazy. Custom Keystones can be made as well, just make sure to say what it is and its power in the description, and the decoration could be added in a render if one wishes. I'm not sure of the deadline yet, because only a few people have commented here about joining, and it will depend on the number of entries. I don't think I said this yet, but if you choose character switching, including the other characters would be recommended, either the same way as the other characters or in the description.

Phew, that's a lot! Thanks for the list ngriffin, it'll save me some time!

Since the large baseplate for the Story Packs in not in the database, should we just replace it with a couple of others? Or leave it blank?

The large baseplate as in not the toy pad? You can do either.

Yeah, meaning the grey plates with the hole. Sorry, I wasn't specific. 😛 Thanks!

I posted my first entry. I made a slight pun with the title that probably will fly right by most people, but I hope it qualifies! (the model; not the pun) 😛
http://www.mecabricks.com/en/models/Qb82xM0Mj1z

Hehe, I got it... Looks great!

I saw it too. The only reasons I wouldn't qualify it was that I noticed that the antenna dish thing is just kinda floating there, without any connection. Did I miss something, did you forget something, or was that intentional? And the hinge plates on one (The one with the floating cheese slope) of the alt builds can't be that way for real. And the fusion of the leaves on the tree.

Huh. I checked the model (in the library) and I saw none of those things. The dish is connected perfectly well (that took me a while), and the palm leaves are connected legally (classic 90's LEGO technique), and the alternate builds (while extremely flimsy) are connected with studs. Am I misinterpreting your comment? Or is there a bug of some sort?

Well, I don't know how to post pics, but let me try to be clearer. On the radar dish, the phone doesn't seem to connect. The palm tree leaves, one was rotated too far and occupied the same space as another, but that's minor, because you just need to rotate it. The alt builds, the Rebel Burst Fighter had a cheese slope that was above the panel I assume it was supposed to be attached to (The 2x2 with one stud), and the sides of the 1x4/2x2 hinge plate was going through the brick. Make some things transparent and turn on the outlines, that might help.

Thanks for the clarification! I saw what you meant for the tree and Burst Fighter and altered the parts placement slightly (it looks a bit better now, actually :-P), and, although I'm still unsure what the issue was with the dish, I reworked the design slightly to make it more feasible. Hope that fixes everything! 😃

Ok, that fixed most of it, the part on the radar dish is where the phone (https://www.bricklink.com/v2/catalog/catalogitem.page?P=6190&name=Bar%201%20x%203%20(Radio%20Handle,%20Phone%20Handset)&category=%5BBar%5D#T=C) connects to these (https://www.bricklink.com/v2/catalog/catalogitem.page?P=15712&name=Tile,%20Modified%201%20x%201%20with%20Clip%20-%20Rounded%20Edges&category=%5BTile,%20Modified%5D#T=C).

Oh, ah. Okay. That was entirely my fault. Final draft now submitted. Sorry for the spam! 😕

No problem.

Hi, I just wanted to let you guys know that I haven't (completely) forgotten about this. 😛 My entry should hopefully be up within less than a week. 😃