Hi Shawn, all good questions, but you don't need to worry. Once you buy a logo here, it's yours. All rights to the design go to the contest holder. You can change it in any format you'd like after the contest. Obviously, it's in every designers interest and hopes that you will still need their "help" after the contest is over. The designer should deliver the final accepted design in various file formats so that doing signs, t-shirts, embroidery etc… will be easy for you. The designs will be in a vector format meaning that you will have top quality no matter what size you'll need it in. Be it on a shirt pocket or for billboards on the highway, the quality will look great. I always do the designs so that it's easy to separate each element. If you need the cactus only, you can take him out of the design and place him where you need him.
I hope that answers your questions. Let me know if I can help out anywhere else.
Dave