You can embed photos, videos, and recordings of unusual or exciting birds to your checklists.
If you have a photo sharing website you can find the URL of your image and insert it directly as:
HTML code: <img src="http://your-photo-sharing-site/your-photo-name.jpg" />
If you use Flickr you can use the "share" function and copy the code.
Here are two things to remember:
1) Add the photo to the species comments section for each species (NOT checklist comments).
2) Use "medium" size (about 400x400 pixels).
3) Use no more than 2 photos per species.
Example eBird list with several photos embedded.
There are two pages on the eBird site that will provide more details.