Desktop.ini?

So pretty much anything on my desktop that isn't there by default?

Yeah, pretty much. I doubt you'll mess up your computer, though it might just make everything look ugly. I'll give you an example of what desktop.ini does. I use a program where I can skin my own folders. As you can tell by my name, I really like bacon. So, I have little slices of bacon pictures in place of the old folder icons. After this customization, desktop.ini appears. I just set it as hidden and forget all about it.

It's not worth deleting really. Just set it as hidden and don't think about it too much.