Haha, and here I thought fungi were asexual.
Okay...I'm a little picky when it comes to sprites. It's not uncommon to start off a little slow...Zal's posted a great link there, there's a lot of awesome stuff by people in galleries and such. If anything, I think you should learn basic techniques first:
http://www.spriteart.com/index.html
http://petesqbsite.com/sections/tutorials/tuts/tsugumo/
http://www.derekyu.com/extras/pixel01.html
There's some tutorials to get you started.
Starting off by editing other work is good. You'll get to observe how others do their sprites and all that good stuff.
I'll offer you basic advice:
1. Don't save as JPG. JPG compresses the image by 8x8 pixel areas, and a lot of the crispness and image quality of spriting and pixelart is lost. I see you have some JPGs and others PNGs...PNGs are good. Also, BMPs seem good, but they're huge, so don't use them either.
2. When you make outlines, make clean lines. Sometimes you have "stairstepping" or jagged pixels that touch each other. You can see the difference by making a line in MS Paint versus drawing with the pencil or brush tool. The kind of line that you want is the kind of line a line tool creates. I can't explain this better, really...
3. Unless you're making a large pixel piece, stick to 16 colors (one is reserved for transparency, so that's 15 colors on the actual sprite). It's the traditional amount of colors in a sprite, and well, using more colors is kinda unnecessary because you won't see them all.
I guess that's all I can tell you for now. You do have a lot of potential, so you should stick with it. Good luck !