These might be the last ones I do for a while, for reasons involving free time issues...
I have to ask, what is your method of spriting? do you draw the pokemon on paper then scan it and sprite over or do you just sprite on paint or whatever you use straight away. Anyhow wonderful project this has inspired me to start spriting good luck with this.
Well first I set a drawing region limit depending on the size of the Pokémon, usually choosing between 40x40, 48x48, 56x56, and 64x64 (give or take a few pixels for all but 64x64 since that's the max GBA sprite size limit). And then I just draw it while looking at the official art(s) as a reference, or in some cases such as Voltorb and Fearow I'll look at a past sprite and use the pose. I don't do any tracing at all because those tend to produce ugly results at these tiny resolutions.