The Che Guevara one incites a lot of emotion for me. Perhaps it would be a better subject in black and white, where the photo is really about the emotion of the person who painted him on the wall (obviously a passionate person to endorse his viewpoints so much as to paint Che on a wall).
I think some of your photos lack a "wow" factor, as do most of mine. But that's not bad. You seem to be grasping some of the more fundamental techniques (not rules) of composition, and that is good. The caterpillar and the Che Guevara ones are my favorites (which is funny, cause I get two totally different feelings from them, lol). I will second what people say about putting things in the very center of your image (the center of an image is kind of a no-man's land for exciting, eye-drawing objects), but other than that, they show good comprehension of basic composition, and are probably better than I could have done!
Edited to add: With the Che Guevara ones, you could do it in black and white, and then add selective coloring in for each of the different pictures of him, each in a different color! Its not my photo to do that with, but I bet it would really give off that, "Viva revolution!" feeling he's all about.