There's no perfect search method, especially when you're looking for images. Even when I have searched before posting, I know that I've posted several images which I subsequently discovered had been posted previously. No one is going to get castigated for reposts, although
Tourmaline does a good job of pointing them out
.
Where an image no longer exists, you may find that Google has cached a lo-res version which at least allows you to see what's missing. This also reinforces the point I made yesterday about including descriptions with images. We lost a load of images when USC changed their storage method, but I've managed to track down many of them either through the accompanying description, or by using reference numbers in the links. When a member-hosted picture disappears, the accompanying direct link to the original image can be vital. I know it can be a pain including a direct link for every image (I admit to being lazy myself when I'm referencing the City Directories and Google Street View), but it's just one more thing that can help to preserve the cohesion of this thread.
With reference to
MichaelRyerson's
point about un-hosted images, I entirely agree. Please use an image host such as Flickr, ImageShack, Photobucket etc. when you're posting pictures, and especially avoid hotlinking to eBay images - they disappear very quickly. If the idea of using an image host sounds scary, it's really not. You can set one up in minutes, and there's bound to be someone here who can help you out.