Carving your own stamps is quite entertaining and, once you get done, it's great fun to try out your stamp for the first time. I usually have to go back and clean up quite a bit, as it's easy to miss spots here and there, but that's part of the fun. Many people leave on the bits to add more of a rustic "hand carved" look to their images. Personally I like them cleaner, however, and will attempt to clean up all the missed bits.
I used the soft rubber (similar to erasers) stamp carving material that you can buy at arts and craft stores, but found there is quite a difference in the quality. I ordered some from Dick Blick but found them way too soft and "rubbery" for my taste. It was hard to get a clean edge at times. I definitely won't do that again, although I ordered a dozen small sized pieces to get a better price so am stuck with them. They're fine for the larger designs with less detail, such as the branch but are harder to use for the more detailed designs. It's worth the extra money to buy the higher quality carving material.

The images in the picture are the ones I've carved so far. The one on the far left was my own design. The upper right one is supposed to be cracks. I wanted to give a look of cracked paint to my pages. I think it kind of looks ok, but the lines could be a bit thinner, although that's one thing that is rather hard to do with the soft rubber is getting nice thin lines. The other 3 are designs from Dover books, which I traced and changed a bit here and there to suit myself.