Sushi not good for your corn...
I kept garters for many years and never even fed them fish. As they got larger, they ate extra large nightcrawlers. Everything I have read about feeding fish recommends not using "feeder" goldfish because of the potential for parasite and bacteria exposure. I have some friends who feed their western hognose bits of fish sometimes but it's always farm raised trout... pretty funny!
Eggs would also not be a good choice as corns lack the rib bone appendage to crush the shells.
When I was a kid, I kept a lot of locally caught snakes and fed them whatever I found that were listed as proper prey items for them. For instance, with my kings, I fed them lizards, baby birds, mice... anything that I could catch. Now, you will get a lot of arguement from the herp community because keeping pet snakes is a lot more sophisticated now than it was "back then". Also, feeding wild food will expose your snake to parasites and bacteria. Now, these things are things that your snake probably has already been exposed to, having been removed from the wild. The difference is that in the wild, the snake is not in a confined situation and it's body is better able to deal with these parasites and bacteria. In captivity your snake may have a plush place to live and won't have to hunt to find food, but it does have to contend with types of stress that, in the wild, it would never encounter. Also, living in a small enclosure concentrates any bacteria to the point where they can and often do pose a threat to the snake's survival. So... now that I have told you all that... I will tell you that if you can afford to, it would be best for you to take the snake's poo to the vet to be checked for parasites and bacteria (something that is always recommended for wild caught animals) and feed it only commercially raised rodents. BUT--- if you do not have access to the means to do this(you know $$$) (as I did not when I was a kid catching and keeping snakes), use common sense. Keep your snake's cage REALLY clean. Don't let any poops stay in it at all. I saw how you fixed it up nice with rocks and stuff but I can tell you, your snake will feel much better if it can bury itself under something. Trade the rocks for paper towels, bark, aspen (at Walmart its only 2 bucks). Easier to clean and will look fine. You can keep the cool skulls and stuff (love the coon skull). If you have to feed it lizards and what not, make sure you don't collect them in places where someone could have sprayed for pests.
Hope that helps. There is a lot of really good information on the internet that will tell you about corn snakes so check it out and keep coming here and, most of all... enjoy that pretty snake!