Coloured pencils are a fine choice of medium (one of my favourites to use, actually), though I would still suggest to work on tightening up your colouring, to make it a bit more solid. And while graph paper is alright for the time being, I would suggest that in the future to look into scaling up your sprites onto a more professional surface, such as Bristol board. It may take some practice and several pieces of paper before a perfect scale is figured out, but in the end it will be worth it for portfolio pieces.
At conventions and collectors' markets, there will be a market for these sprites. You have a potential gold mine in your hands, you will no doubt attract many customers once you put your work out there. However, since many of us are quite capable of using scissors, X-Acto knives, rulers, and cutting mats, attracting buyers for just the sprites alone may be a bit tough. Offering a variety of products will bring in a variety of consumers. I mean, who wouldn't want a Protoman sprite pin for their messenger bag? Or a Zero sprite magnet to hold up their grocery list? If you attach clips to the backs, you can make barrettes, too. I know I would wear a Metal Blade in my hair.
At Ohayocon one year, there was a dealer selling anime emoti-symbols. These were very simplistic, merely laminated drawings with a clip taped to the back. The dealer was charging $2 a piece for these things. And believe me, these were selling quite well. Another dealer was selling text smiley pins for $3 a piece. If you were to turn these sprites into pins, magnets, stickers, clips, t-shirts, etc., I bet you would easily make $100 or more on them.
As for requests... I don't have any at the moment.