layout I think more depends on what you need to put in there, like my reptile room which is 9x9 with a 2x4 nook, I stacked all the racks on one side next to the nook, build shelves for bearded dragon babies in the nook, opposite side went the bigger snakes, i still have room to open the doors. and another wall got the adult bearded dragon cages. just gotta figure out how to make everything work.
heres a thread I made when I first built it, I got alot more in there now. more home built cages, I should take update pictures.
Reptile Room
suggestions are defently make sure you got a way to cool and heat the room if needed, heats usually easy since you can just plug in a electric heater. but the only way I got to cool mine is with the houses a/c. 95 degree days can do a number on your reptile room.
most people say put in a fan to keep the room at the same temp, tho I did not lol.
I love my timers turns all the lights off at nights and other turns on the red bulbs for the dragons.
If a wash tub isn't close you might want one of those
for my rats I built a small sealed room in the basement, bathroom fans venting outside
Rat Room