That is true...

I am having the same problem. I changed the permissions to 777 and I also created the theme php file and am still only seeing the initial four themes. Did you find a workaround or a solution for this?

Well, the reason for a theme not showing is that there is no description for it. I do not know what the "theme php" file you mention is. You must have either theme_description.php or theme.txt present in the folder. (The post above was not correct vs. the second file's name.)