Since my office doesn't have a dress code at all we don't actually have casual Friday, but I've noticed everyone seems to informally observe one anyway. Also, as today is Geek Pride day* it seemed like a good time for one of my work-appropriate geeky t-shirts.
Domino's Dollhouse. If you haven't heard of them before I recommend checking them out. The styles are generally pretty gothabilly and punk and some randoms, kind of reminiscent of early Torrid, however totally unlike torrid the clothes are well-made out of decent quality fabrics (I have seen way to many polyester a-line skirts going for 50$+ at Torrid. There is a lot of discussion about the advisability of wearing dark colors in summer, but synthetic fabrics are the real enemy). I also recently got these grey and black striped tights (thigh highs, actually) which are really great subtle stripy tights. I included the weirdly moody photo below just because it was the only one where the tights showed up.
Shirt: Think Geek
Skirt: Domino's Dollhouse
Tights: Foot Traffic brand via Sock Dreams
I also wore my new favorite hairstyle: a dutch-braid bun. It makes it look like I have a huge amount of hair and is classic looking but still interesting.
*the combined holiday commemorating Towel Day, the Glorious 25 May, and the release of Star Wars and celebration of all things geeky. Towel Day may be my favorite but I have yet to figure out how to visibly incorporate a towel into a work appropriate outfit, so that's strictly after hours.