You can just use *; there is no need for .. File extensions are not special on Unix. * matches zero or more characters—including a dot. So it matches foo.png, because that's zero or more characters (seven, to be exact).
Note that * by default doesn't match files beginning with a dot (neither does .). This is often what you want. If not, in bash, if you shopt -s dotglob it will (but will still exclude . and ..). Other shells have different ways (or none at all) of including dotfiles.