Hi Creep, I can't help with increasing your personal space, but have you been optimizing your images? If you process them through tinypng.com, you can fit more of the images into the same storage space. Or do you have a friend that will allow you to store the images on their account? They would need to make their models public to share the textures, but it could possibly double your capacity.

Edit: Another thought... if your part doesn't need to be of the highest resolution, you can drop your resolution down. Going from 1024x1024 to 512x512 will cut your file size down to roughly 25% of the original size. For instance, the 2x4 tile (87079) and 1x2 tile (3069) both use a 512x512 texture. Your 1x2 tiles could have the same quality as the 2x4s if you dropped them (1x2) to a 256x256 texture size. It all depends on how close you're going to be looking at the parts and how much detail you need.

Unfortunately, user texture storage cannot be augmented, so if the project is entirely within Mecabricks, it is impossible. However, if rendering in Blender, it is possible to create as many custom parts as possible, export them to Blender, then delete the parts you have made along with their textures. Then, repeat the process as many times as needed until you have all your parts.

Thanks, I'll try optimizing the textures.