Images not displaying after transfer to temporary site ~username
Sorry, I just re-read the question and realised I misread it before.

Try setting your base path in the .htaccess file and also the base path in the settings.php file. (actually I think I'm confusing myself. I'll leave this here anyway.)

Previous answer

Are you talking just image style images or all images?
Can you look in the source of your page and give an example of one of the file paths that is not loading properly?

I know you have stated you have already done some of these, but this is what I would try.


Check a few images by looking at their path in the source and checking on the server that they exist in that place.
Try going in your browser, directly to one of the files, for example yoursite.com/sites/default/files/yourfile.png or whatever it is.
Check permissions of files directory and also the temporary files directory, which must exist and be writable (the status page should alert you to these anyway).
Try saving your image styles to force them to regenerate your images, and clearing your caches again.
Check files .htaccess
Check your watchdog logs for any errors that might be related (any unrelated errors should be investigated too.