The to one, the orange one, and the bottom one are cool. did you digitally paint the clouds in the orange one? If so then well done =)

Last one is good, but some of the brushing is kinda 'in the wrong place' - bits just look like you've gone mad with the paintbrushes :P

The top one is nice the smudged bg actually looks ok, it's kinda done in a grungy way, maybe a lil' more contrast though.

Overall fairly nice