first, i just want to tell u that it never matters wat d topic is but d procedere matters that how would you do it. choose any topic on which you r having sufficient raw material so that u vl not rush towards collecting material in thesis rather analyse the material....nd have best possible results......

Other than that, if u don't afraid of the scale of the project.....i suggest u to go for lighting schemes which itself vl incorporate other topics toppings like u can talk about wall finishes, flooring, artifacts etc. as well.......which in future vl benefit u wen u go for any interview or P.G. courses......am a civil Engg. in d market and hold interviews myself for interior proffessionals.....