My suggestion is mostly for the lighting.
On a real gas station, youd expect poeple mostly coming to gas up, so you should put in light specifically for that reason, around the gas tanks and to light up the way towards the inside to pay for it afterwards.
Also, one might need to get into the garage, so a bit more lights on it and a sign, either on top of the roof that is over the gat tanks or one that is seperate near the road would do.
Inside, dont use spotlight type lights, rather go for the "flood" lightning that comes from fluorescent lights.
Also, might i suggest a beer neon sign in the windows?