This thread may be of use
Photo Posting How To
I could update it to include a Flickr tutorial as well if that would be helpful?
EDIT
Another way to do clickable thumbnails is to first get a small version of the picture you want to post. (You can somethimes do this by right clicking on the thumbnail in flickr and choosing
copy link location)
Then open up the image insert button in the editor here on TBN (5th from left in advanced editor)
Click in the box and press
Ctrl + V
Then click OK
Then highlight the picture in the editor. (You may need to click just after it and then hold down shift and press the back arrow)
Then go back to flickr and get a bigger version of the photo up. Right click on it again choose
Copy Link Location
The go back to the editor on TBN and (making sure the photo is still highlighted) click the link button (the world with a paperclip below it)
Paste in the new code you just got (
Ctrl + V)
Then press OK
You should now have a clickable thumbnail. This is basically what PhotoBucket does for you.
I will look at Flickr and find out how to get clickable thumbnails like Photobucket.