Good luck to you.
Here's a few suggestions.
Don't spend a lot on decor. You need to make that place look like a hole-in-the-wall. Que is always better at a BBQ joint than at a BBQ Restaurant. If you can find a laminate floor that looks like distressed wood, you'd get an economical and code compliant floor that is BBQ joint worthy.
Get rid of all those chrome stools, and get some garage-sale chairs. Make the walls look old. If it were me, I might even park a smoker in the dining room and smoke the room out for a day or two.
I'd lose the plain white ceiling, too. Maybe some fake tin tiles, or better yet, some re-cycled tin tiles.
When you get around to replacing the siding, think about materials like recycled corrugated steel and barnwood.
A BBQ joint should be clean, but not pretty, IMO.
Sorry for rambling. It is the Art Major in me. That, and the BBQ joints people tend to talk about are, basically, clean and sanitary dives. That kind of eating environment just seems to set the right mood for eating smoked meats.