First of all almost all wheels are the same when you are a beginner, it doesn't really matter as long as the roll. Later you will grow to be picky (maybe not)... For your first set of wheels a size 54 mm [Very common Size], 99a hardness [Standard] is a good pick.

Size: To choose your favourite size is pretty hard if you haven't tried out big or small. When you first start try to get 54mm these are the average size, plus most people end up liking this size the most too. If you have a chance try out some one else's board, with different size wheels, do a couple tricks and see if you like them. Size preference doesn't matter unless you are really picky, then you will just have to learn over time. As I said 54mm wheels are good to have for your first set.

Pictures: No point to these on wheels in about of week of skating they will rub of so don't even look at this. The colour doesn't rub off though, so if you want some red wheels then get some if you want because the colour doesn't wear of really easily. Colour has nothing to do with riding, just how you want your board to look.

Hardness: Once you get fairly good, this might be a key factor of choosing your wheels, if you want your wheels to last really long you want something hard, 97-101a are hard wheels and these should be your first pick. Harder wheels last longer then softer ones as they don't chip or get flat spots to easy (Flat spots: when you do a power slide or blunt slide and you wear down one spot on your wheel and it turns flat). I think harder are better and you should pick them. All wheels are 99a unless noted otherwise, that is a good pick for wheel hardness.

We might provide you with more info but for now this is all we are going to give you.