Over the course of a couple months last year, I picked up a couple of very different Power Girl sketches done by the same artist, Chris Foreman. He's on Facebook, but that's just his personal account. I don't think he has an art Facebook specifically, like many artists do. There is a fair amount of his stuff on eBay, both licensed work and unlicensed fan art. It also looks like he takes commissions, as he's got videos on Facebook of him working on them.
I'd been watching this first card for quite a while, and I finally picked it up. Sometimes it seems like sketches sit on my Watch List for at least a year before I buy them. The listings usually cycle out every 30 days, and there are some that I know I've re-watched at least a dozen times. Anyway this is probably my favorite of the two. It's a little more dynamic, and I like the bright colors and cartoon-style linework. This one is on his personally-branded card stock and done in 2010.
This one is from 2014. I got this one directly from the artist on eBay, but when I went back to look at the transaction just now, it said he is no longer a registered eBay user. It's done in a more realistic style. It's a pretty cool sketch, but I think I like the first one better. Others may disagree. I may try to pick up some more of Foreman's art in the future.