Q1: I want to use this sprite, how much?
A: I unfortunately cannot allow you to buy the sprite because someone else requested it. If however you ask the customer for permission and if they allow it, you are free to use for display but not distribute the sprite.
Q2: Okay I got your sprite so what can I do with it?
A: As soon as you pay for your finished request, you along with me jointly own the work. My rights include credit as the artist and displaying it. Now for you, you reserve the right to display and distribute the sprite as you wish. Neither of us can resell this work and you can't modify it. This does not mean you can't place it among a banner or something similar.
However, someone else who has been permitted to use this sprite cannot distribute it to others.
Q3: Hey, why won't you answer me? Answer me!
A: Woah, woah woah. Relax. There are one of three reasons I'm not replying to your query immediately, and that is:
A) I'm sleeping.
B) I'm currently busy or at a place in time in which the internet/my workstation is not available to me.
C) This is to assume the worst has passed; I am currently in a position in which I won't be available for a long period of time.
So wait a day at the least and I'll get back to you. In the event that C has happened, prepare to be surprised sometime down the track in a few months.