I agree with Pam, don't redo your first ones if you go scrappy just add more fabrics to the mix. I'll often use the traditional red or yellow center square, but not always. I've used all the same and all random. Also I've used bigger or smaller squares than the logs for the center.
If you decide you really hate those blocks, I'd probably just applique a square of a different fabric over the top.
Typically I work in a scrappy style and I usually make a few extra blocks just in case the fabrics aren't behaving nicely. Sometimes my favorite blocks are the trouble makers and don't get used! I used to just have orphan blocks but nowadays in that case I'll put just them in the backing somehow. So making more is always an option.