An extension born as a request from my friends Goofy and Efdur from babelzilla.org, My Image Here allows you to replace an image on a website by selecting an image from your own computer.
All replaced image references are stored in the new Firefox 2.0 SQLLite storage implementation, and will therefore remain replaced untill you remove the reference again. So you can clear your cache, restart Firefox, etc. without losing the pictures you had replaced.
I am not yet sure as to how usefull this extension will actually be for you all, but just have a look. My Image Here was initially intended for web developers only, but after releasing it on babelzilla it appeared to be great fun to just play with it as well.
How do I use it? Well, you just right click on any image on a website (as long as it is a html IMG element), and select [Load My Image Here...] from the My Image Here context menu, and select the image you want to see instead of the current image, easy as that.