DISCLAIMER: Since this is a very dangerous feature that could violate TOS, I’m not going to release the code to anyone. This is a proof of concept and will never be used in live production.
I’ve developed a way to load any image from the internet into Roblox using a simple NodeJS server. It’s very CPU intensive and would be extremely impractical to use in a game, but it works.
Heres a video…
Ignore the image inversion, I accidentally flipped the X pixels.
Wow! This could save Atleast 1 hour of my development since I use so many textures!
Would be cool if Roblox would allow us to enable an image filter. This might help reduce time consumption on just uploading and processing images. Very cool though!
I created a program in C# that does the same thing. User uploads a picture, and it is converted into a module. The module builds the UI.
There isn’t much you can do about this.
Are you just rendering the images with a frame per pixel?
I managed to do this once, this takes a huge amount of time to load. Think of around two hours for the server to clone a tiny frame per pixel for an image that’s 1000x1000 pixels. (Don’t think of rendingering HD images, that takes wayy longer) 
Maybe I could have tried pipelining the build from the pixels, for example pixel line per line, but then we would still have 1920 scripts running at the same time for a full HD image. 
Kind regards,
Jonas