The red shirt says on the front "I'm not pretty...." and is decorated with all of the horcruxes. The back side (no picture ;[) says "I'm evil!" I'm not completely sure if he's evil or just secretly girly inside.
The black shirt has a list of influential characters in the style of the Jabbawockeez's shirts, with all but a select few letters in gold or yellow. The remaining letters in red, when read from left to right proceeding down, read "NEVER SAY DIE".
Worn to the midnight premiere of the final HP7 part 2 movie.
One last thing: I used a heavy cotton shirt from a crafts store and hot-glued on all the felt pieces (which didn't work fabulously -- I should have sewn it but I didn't have the time), and the shirts were incredibly warm, so if you're naturally a very warm person, consider choosing a different material than felt, a lighter shirt, or sewing instead of hot glueing.
Brainstorm for slogans, pictures, or styles that you styles that you may want to apply to your very own Harry Potter shirt. For one shirt, I decided to make the first shirt trendy so I could wear it post-premiere movie date. I decided on the Jabbawockeez lettering since it's a popular style around my school.
For the second shirt, I based it off a humorous doodle I had done during one of my classes last semester.
Next decide on the colors you want to use for the lettering and/or pictures. For the Jabbawockeez shirt, I wanted to represent Gryffindor by choosing gold and yellow letters with red letter accents. I used the gold and yellow (randomly) so the shirt would have more depth to it when looking at it. Finally, to make it pop, I used a black t-shirt I bought from Joann's for $3.50.
Cut out all pieces of the felt (letters or pictures).
If you decide to go the easier route, use a hot glue gun to glue the letters down. NOTE: after a run through the washing machine, some of the letters will peel off a bit (though not completely). I recommend sewing all of the pieces onto the material, but due to time constraints, I didn't have this option.
Enjoy your awesome new Harry Potter shirt!