Hello.  I can't seem to change or remove the logo on my site - the big infinity sign with 'All Things In' in orange in the upper-left.  I removed all images from "Icons and Logos" so there is nothing listed, but the image still appears - and I have cleared my browser cache and even used a computer I have never used to connect to the site (so there would be no cached images) but it is still there - community.allthingsin.com - any advice to remove it?  Also, what are the best dimensions for that image?

You need to edit your theme in order to remove that. Its on the logos tab of your theme, rather than in the icons and logos section. 

 

The size of the image doesnt really matter. It will resize as needed on a default unaltered theme