LMAO I know this is very old and OP probably found an answer already, but for anyone having the same problem:
The cash shop's description and image are based from your item_db table as well as your iteminfo.lua(idnum2 txt files if you are using older clients)
Just make sure to upload your data.grf as well as custom grf in cora/www/ROChargen/client/ folder
If you're using newer clients that uses iteminfo.lua, upload your iteminfo.lua in cora/www/ROChargen/client/lua files/ fodler
ifi you're using older clients that uses idnum2 txt files intead, it should be included in your data.grf so no problem.
Next thing, make sure in your settings.php find
'use_iteminfo_lua' => true, // set this to the correct value