Honestly, I have no idea how to tag this beyond gundam really. I just wanted to know where it came from 8v
I got it off a guy's MAL profile, so yeah, definitely not a source. Maybe do a search for it on pixiv?
The earliest source of this image that I can find is that it was for a card game in 2009, and that the artist is Naochika Morishita. The image was cropped when put on the card though so I still have no idea where did the full image come from. Not from Naochika's artbooks as far as I can tell. One more thing, this full image has already been on the internet since at least 2010.