"I just ask that you credit me in some way for the assets. "
Isn't buying the asset credit already?
Viewing post in Pixel Button Prompts! (Keyboard/Gamepad) comments
Buying the asset gives me money, which is great! But not credit. Credit would be a reference to Retrocade Media somewhere in a credits screen. Even if briefly, with a mention of the assets used (something like, Gamepad Icons - Retrocade Media)
Its not required, but giving credit like that is a nice thing to do. I credit Endesga on all my projects, as he created the color palette that my projects use.