I like the ones with white background (ultimately this logo will be transparent BG) because of clarity.
I like the character you created, but it says "Business Guy" or "Family Guy" instead of college student. I'd like to see some character there that looks younger or less business (the polo shirt and glasses don't say "college" to me). Also, his closed right hand might have a "thumbs up" to communicate happiness here.
Entry #19 is my favorite for the site, and Entry #20 would be nice for a shirt.
#32 is your best to date! Can you put that on white background and make the tagline black or blue (slightly larger font) Maybe the circle around the guy needs to be blue like #33 after you make those changes--I'll let you decide what you think looks best after the BG change.