I don't mean to sound harsh, but if your a college student for graphic design and this is your work, then unless you just started you have some problems. First, one thing I noticed about most all graphic design students is that they have a really clean style which comes from techniques learned as designers that inadvertently wind up in their work. I can usually tell what profession someone is from by their artwork and by the looks of yours it seems to me that you are still in the amature artist stages and haven't really developed into a particular field of work, however I do see the beginnings of a designer in your linework. My advice is to ditch the gradated shading that is the sign of a illustrator/fine artist for now and focus a bit more on solid color shading, study some classic comic work if you need ideas.
On the other hand if you are more interested in the illustration/fine art aspect then I recommend you buy some traditional media and start learning those techniques and some solid color theory before going digital, trust me, you will see a massive improvement in your art. Also study some classical paintings for composition, if you think that's too stuffy then look at some of the work on conceptart.org, a lot of the artists there use classical composition but their work is a bit more modern so you will be able to relate easier.
Other then all that, It's always nice to see an up in coming artist starting to learn the trade so keep at it if this is something you really want to do. There's not much money, but its definately a enjoyable career.