No iguanas, and no turtles that grow too big to live in a 30 gallon aquarium. I see dozens of abandoned iggies and red eared sliders. Remember that your customers are not for the most part herpers. Iguanas are awfull pets for non-herpers. Corns, balls and beardies are good pets, dont cost a fortune, and should move well for you. Some milks and kings (I like hondos in particular) are not too bad for beginners.
While aspen is a great substrate, mulch or bark will look better, and that does matter. Carry both, recomend either, but use the more natural looking one for your displays. Another good idea is to have care sheets around for everything you sell. Not only for your customers, but for your staff. You should know what's captive bred, and what's not, and be honest about it. Nothing worse than being told it's captive bred when you know darn well it isn't.
1 adult bull snake: "Dozer"; 1.1 juvenile bull snakes: Oscar and Phoebe; 3 baby red-sided garters; 1.1 macklot's pythons