I really like this idea, and I’m someone who hates disrespectful ads. A small, non-animated tile—ideally advertising something I’m interested in—sounds like something I wouldn’t mind seeing.

One thing: I really hope you don’t plan on making these things wiggle or anything. That’s exactly the sort of obnoxiousness that prompts me to block ads, and I think that would defeat your stated goal of unobtrusiveness here.