After years of using a particular set of illustrations for my company's brand, I finally decided to stop using them. I really liked these illustrations. To me they were a bit like "Picasso meets Life is Good." They were unique and joyous. Also, I have always loved the idea of using custom illustrations instead of photos.
But we had a number of people react strongly in a negative way towards them and I think people weren't thinking of us as an "agency" with the characters. For months I had worried about them too. I surveyed my customers to get their opinions and across the board the feeling was either "I don't like them" or "they are 'okay'." - no one checked the "I love them box."
We decided to switch to a "rivers" theme or more a "brick and rivers" theme. It's a bit more traditional but I think when people are making decisions for their company they are a tad risk averse - they want to see a site that looks more like the site they are going to have built.