Thanks so much for your comments.
Yes, that's basically my pattern-making process. Often I can find cute store-bought cookie cutters that will serve a purpose in a gingerbread project, but mostly they're for decorating touches (stars, hearts, trees, etc). Everything else is from scratch.
After deciding what the gingerbread project will be, I draw it out and make a complete mock-up by taping together what I cut out of cereal boxes. These then become the patterns. When deciding on smaller patterns, I try to keep these designs really simple. First I draw them on white paper which I glue onto the inside, non-colorful side of the cereal box, then cut them out with scissors. Manicure scissors can be helpful for tiny details.
The shiny side of the cardboard pattern, liberally dusted with flour, is placed onto the rolled-out cookie dough, and a sharp knife, also liberally dusted with flour, is used to cut around the pattern. Understandably, the larger parts are relatively easy to cut out, while tiny things, like kittycats, not so much. But with patience and a little luck I usually end up with something I can use, and everyone seems to enjoy nibbling up all the "mistakes".