Pretty much any Linux distribution you can think of can fulfill all of the software requirements you specify. It will just be a case of installing them via the package manager that comes with the distro.
- Photo editors: look at GIMP, F-Spot
- Video editors: try PiTiVi
If you're new to Linux, you'll probably want to go with one of the big four distros: Ubuntu, Fedora, openSUSE, or Mandriva. Ubuntu is probably the most popular, or has the most hype at least.
As you're interested in media, you may also like to look at Linux Mint, which basically respins Ubuntu to make it work a bit nicer with multimedia out of the box.
You can do ssh and BASH scripting on any version of Linux. You'll be able to ssh into your iPod Touch with no problem.
When it comes to speed and ease of use, it's more important to decide upon your desktop environment than your distribution. The big two are Gnome and KDE. They're both very capable and featureful, but I personally find both of them too bloated. Xfce is a good compromise between speed and ease of use. There are faster environments out there, e.g. fluxbox, but you tend to compromise somewhat on ease of use for speed. enlightenment (e17) looks sweet and runs fast, but isn't always easy to set up from your package manager.
Overall I'd say give Linux Mint or Xubuntu a go. They're easy to use and to install new software, and you'll be able to easily install a different desktop environment from the Ubuntu repositories if you're not happy with the one that comes as stock.