Parker,
Now worries-- I didn't use anything from the HTF.
I made my own graphics for my own Atlanta forum and uploaded them to cafepress.com. They're all Atlanta specific and have nothing to do with the HTF.
They turned out quite nice. Cafepress has image creation and uploading guidelines ("use AAA by BBB resolution", etc.) which help the novice (namely myself).
One note: they have a warning plastered everywhere that "What you see is what you get" which one should heed. If your image looks like garbage when you make it, your t-shirt will look like garbage, too.