There are several things you can try as a startup to build on this idea:
Aggregate: aggregate all the logos, products images et al of companies and tag them with useful metadata. Link your service to content recommendation service like Zemanta so that they can help to channel your images to bloggers who want to use them. Create a affilitate link whenever possible to each of the images. That will be the revenue model.
Analytics and Brand Monitoring: You can also provide analytics service for this new form of 'product placement'. Beyond providing basic stuff like viewership, click rates et al, what is more interesting is to be able to let companies know whether the sentiment of the blog that uses the company's images is positive and/or negative.
Using Image as Context: Create a metalayer for more information and even discounts that can be tagged onto the image. For example, browsing over the image might bring up other blog posts that use this image or news articles that related to this company. The important thing is to use the image as a context to filter the rest of the information.
What other things can you think to build on Dave Winer's idea?