Keep in mind that in the pro listings that your photo/logo will be cropped to square - so you might as well upload something square so you'll have control over what is displayed. Or, you can play around with it and see how it looks on the pro directory and your pro profile. This is the link that I'm talking about: http://www.houzz.com/professionals
I'd go for 1000X1000. :) Rhoda

It appears to be square or close to that proportion. I used the screen size to match the resolution, and it appears to be 200x200 pixels max. on my pro profile. Doesn't ever seem to show up larger than that unless I'm missing it somewhere. Thanks for your input.

The general rule of thumb for photos on Houzz is "bigger is better." Rhoda is correct that it is the proportion that matters most for profile or logo files. If you upload an image file with higher resolution, we take care of compressing it to make it fit and you maintain good image quality. Hope that helps!