Most high quality and lossless image filetype with GIMP?

[mahesh]

Yeah, I know I post a lot but sometimes I just keep having questions..

You may call me picky if you like

I feel like I can spot individual pixels right on and it really annoys me because I keep feeling my artwork is looking low-quality.

What's the most lossless and quality preserving options? I would imagine png is the most lossless, but GIMP also gives me a lot of other options which I don't really know wether to select or not to preserve quality.

So, what is the best quality for GIMP?
My Deviantart
Doin' it GIMP style