Going down a scale, from 15 mm to 10 mm, can work for battle level games but tends to be a personal preference choice. Hovels buildings for 15 mm do tend to be a bit on the smaller side already within my experience. My preference is to stay with 15 mm buildings for 15 mm figures.
On the skirmish level, there is another option - going "big" such as using Bluemoon's 15/18 mm buildings with lift off roofs. Not sure how much they have specific to the Napoleonic era but certainly much that can be readily adapted. The larger buildings - perhaps big enough to even use with 20 mm figures - provides more "finger" room for placing figures inside the buildings.
Sorry, no photos but if you can find early issues of Wargames Illustrated - through say issue 60 or so - you can find lots of images of Hovels 15 mm buildings with figures, not every issue of course but I doubt you'd have to through more than a years worth of issues to find some.