Here's what I found on camouflaged Firefly:

The Polish 1st armoured division had this paint scheme. (Sorry, I dug this info up quickly. I don't have time to research my books further on where this version saw action.)

This one I'm not sure about what model sherman this is. It also could be just an artist's rendition of a winter camo for the sherman. Would be nice though.

And this one looks like the Sherman M4A3.

This one just looks menacing. Another fun one if it fits into HTC's criteria.
I'm not a tank expert. Hopefully somebody can come in here and offer some solid answers to this question.
Obie.