I need help with making a 3d(?) Sun for my Fnaf mod

I'm not really sure how to explain this well, but I'm making a Fnaf mod, and I'm still kind of new to MCreator, I have the basics down, like making textures and being able to make blocks and items and such, but I'm not really sure how to make this sun I made it's own object. I can easily just add it to other block textures, but I want you to be able to place it wherever, kind of like a painting, but when I tried making it a painting, the transparent part turned black, and I'm not sure how to remove that, if that's even possible, but if it is, I'd like to know. I'm happy to use Blockbench if I need to to make it work. Any suggestions is appreciated.