Every one of the photos of shower tents posted thus far are tents that are FAR too narrow. Believe me, you will regret buying something that narrow. No room to move at all, no room to dry off, constantly bumping into tent sides while trying to shower.
I know the OP asked about a home-made shower stall, but if you decide to purchase a shower tent, do yourself a favor and buy a decent one. Stay away from the Walmart stores and get one that looks like this...you won't regret it. I paid $50 for mine on ebay, but it looks like they are around $100 now.
