Eons ago, I used to run spriting contests at Pokerealm and the early Topaz forums. They were pretty popular for a few reasons:

A) The thrill of the competition
B) Helpful criticism (provided by myself) helps you to improve your skills.

The contest, if I decide to run it, will operate in a series of 5 rounds, covering a range of basic Pokemon spriting styles, which includes but is not limited to:
Mixes (combining two or more Pokemon together)
Re-colours (changing the colour of a Pokemon)
Type Changes (editing or mixing a Pokemon to make it appear to be a different type)
What will the rounds be? Anything I want them to be. The difficulty will increase with each round, but by how much depends on the skill level indicated by the first few rounds.
Each sprite will be rated on a scale out of 10, then points given based on where you rank in each round. There may be a prize. I don't know DON'T PRESSURE ME.

Being "good" at spriting is not a requirement, as this is partially to help you IMPROVE. You may surprise yourself with how good you are. I used (and still use) MS Paint to do my spriting, so if you have that, you are eligible to enter. (If you're on a Mac, I can link you to a Mac version of it that you can use.)
In terms of time commitment, don't worry too much about it. I'll be giving ample time for each round to be completed, like 2 weeks. Obviously if everyone submits faster they'll be posted, but there is no pressure to finish.
If you have any other questions about how it will work, I'd be happy to explain.
And if you would be interested in entering if such a contest were held, please say so. If there is enough interest, we can probably start relatively soon.