Just did a new install of IH 4. Everything seems to be working with images appearing in online catalog but the little image previews are not appearing on the Admin Image Handler.
Sounds like you have an incorrect path entry in your configure.php.. (discussed a few posts back in this support thread) Not really an IH4 issue as IH4 does not modify the shops two configure.php files, this is a general Zen Cart setup issue..
My Site - Zen Cart & WordPress integration specialist I don't answer support questions via PM. Post add-on support questions in the support thread. The question & the answer will benefit others with similar issues.