oh yeah the banner in the 3rd post on this page is banner number 500 for the site (currently at 516)
yay! banners! everyone reading this needs to make a bunch of banners!
this is the one I used, I slowed it down a bit so you could see the animation better post-squash:
it's from the attract mode for the original Metal Slug game, that gif might be vertically cropped a bit from what you'd see in the actual game but I don't remember and I'm not going to check