I wonder what you could get in the way of company logos that aren't specifically linked to racing in the real world? Racing planes sponsored by aircraft companies, engine companies, oil companies etc... Airline sponsorships is another possibility where you can certainly get logos.
BV-141 sponsored by Bovril?

Years ago I did some work on adapting Robinson's Brewery artwork for a Tomcat warbird, since their best-known product is a beer called Old Tom.