I tried something new last week for the BOC which turned out nicely. We have been reading Robin Hood, just finished Winnie-the-Pooh, and we watched a movie about Van Gogh and did a Van Gogh style art project, so I wanted to do entries for those topics.
I typed the keyword into google images and found an image I liked, and underneath the image (ormaybe in the sidebar if you click on the image) is a link called "more sizes." This takes you to a page with the same image in all available sizes from big to small - the size is given in the lower right corner of each. I chose a good link for a very small image and printed it for each topic. Then we cut out the tiny picture and glued it on the correct page in the BOC with a handwritten notation.
I don't think it is necessary to have an illustration for every entry, by far, but it is fun to have a few. If you don't have a color printer, or want to save on ink, you can color over your B&W image with colored pencils and they look really good.
We just watched the IMAX movie about the Hubble space telescope and now I want to get that info into the BOC - the start and end of the shuttle program (makes me so sad) and the space telescope. I will be printing images for those things as well. Also I do a half sheet in recent times for family history, so I have some tiny images there - of grandparents and any ancestors we have photos of...
So that is my cheap and easy tip for making colorful images for BOC (or timelines).