Hello, and welcome to pixeljoint.
There is a lot or room for improvement. By the looks of things, you have heard of dithering but a common error in new pixel artists is using it everywhere. The lighting is also quite odd (try looking at references like so to see how water reflects and is shaded.
http://public.fotki.com/Prostokvashino/2_users/08_dimas/interesting_images/raindropjpg.html
The shape is also quite geometric and more cone like than a water droplet.
These colors are kind of what you would see in default paint or its equivilent pallet set. Its rather boring. Try looking here for some wonderful palletes.
http://www.pixeljoint.com/forum/forum_posts.asp?TID=10946
Nevertheless, I hope you aren't discouraged. After time these techniques and whatnot begin to come naturally, so check out the forum and make a topic for your next piece (or even this piece) and more people can actively critique you- resulting in you getting better.
Also give this a look through:
http://www.pixeljoint.com/forum/forum_posts.asp?TID=11299
Thank You So Much!