Drawing graphics yourself is always the better alternative. If you can make everything yourself, do it. I always use original graphics, and the only reason I don't use original music and sound is because I don't have the software to do so. You can always ask someone else to do your drawing, as even though it's not yours, it's still original and nobody save yourself and anyone working on the project with you has seen them before. For example, I'm asking Circy to make a few MIDIs for me, which is a much, much better alternative than throwing in a well-known music from Sonic or Mario.
"how do you accidentally make too good graphics? im really asking"
Excellent question... or not. For example: you make a fangame with your own gfx (i dgaf about who dont like fangames and who do) and then people start searching on ' in which version of the original game had those graphics?'
And... umm... nevermind