Blockquote Cite allows you to add easily cite references when using the blockquote tag.
Download the file and put it in your plugins directory. Activate it. There are a batch of starting images from some of the sites I quote most.
The plugin uses a rather simple, and hopefully idiot proof, way to include images. It just looks in a directory and sees if the domain name is there in the format sld.tld.png. (SLD = Second Level Domain; TLD = Top Level Domain (such as .com, .org, .net, etc).
For example: example.com.png or wsj.com.png.
Not that it really matters, but I've saving all the images using Photoshop using 32 Colors, Adaptive Color reduction, No dither, no web-snap. File sizes should come out to somewhere around 1kb or less.
Thus, you can create your own PNG file and upload to the Blockquote Cite plugin directory.