I've had a shaved head for a couple years now.
I don't know how important shape of head is but if you feel your head and your skull has a defined shape you're probably fine. I know everyone's skull has a defined shape but from what I remember of your pics you don't have a sphere for a head so it should be alright.
Trimmers will do the job if need be but I can strongly recommend these:
http://www.amazon.com/Wahl-Magic-Profes ... l+clippersHaving a pair of actual clippers is useful in general for the amount of hair you have on your head but in particular if you're worried about growing it back to normal length. The multiple length options is valuable for keeping everything a consistent length even as it grows out.
One of the issues you may run into as it grows back out is that the hair on the sides of your head will likely fall flat faster than the hair on the top of your head. This makes the scalp visible on the top but not on the sides - it makes the hair look like it's thinning or shorter/lesser on top when it's really all the same length. The multiple length (guard) options available with a full set of clippers is especially useful here as you can let everything grow out while maintaining a shorter length on the sides than on the top. This should make any transitions much easier to weather.
In general having a shaved head has a number of positives. There's no time or effort spent styling. There's no such thing as a bad hair day. You basically don't need to shampoo or conditioner. Anytime you need a haircut it's free in your bathroom in 15 minutes. If you're comfortable with all that then a shaved head can be phenomenal.