Ok I am not sure what is causing this..... Everytime i install a new RT template I cannot edit the graphics files. I mean i cannot delete the template graphic files or overwrite the files, or chmod or anything. My ftp client always says "permission denied" . I can edit all other joomla templates and files fine.
Another solution is to ftp or use cpanel to upload the template rather than using the joomla's installer. I like to upload them in the compressed form and unpack them on the server with cpanel--much quicker!
The problem is that when you upload the template through the installer, the ownership is "nobody" preventing you from changing the files.
As mentioned above, if you use joomlaxplorer, you will be able to access the files. I like working with my ftp and its helper applications, so I used joomlaxplorer to delete the files and uploaded them as mentioned in the previous paragraph.
Additionally, you can ask your host to fix the ownership of files you have already uploaded--they can do it very easily.
I had that problem with one webhosting service. it's very inconvenient. If you can change your hosting servoce, I would do that. I'm using GoDaddy.com and their shared hosting servers are very Joomla-friendly. I can use Joomla's installer, my ftp client, and dreamweaver.