other than a decent wireless mouse (eg mcrosoft mouse), you wont need much more gadget. As for softwares for editing photos, you can get educational version down the road. just remember say no to piracy for mac softwares.
oh, you may want to invest in a small usb fan or get a table fan to direct air to circulate at it at home. Keeping the mac running cool is one of the best ways to keep it last longer especially when one is doing processor intense operations (ie 3D rendering, batch file processing for photos, etc). It runs consistently fast.
As for the shell case, i would only put on the top cover but leave the bottom alone to allow better air circulation. But thats just my preference. some will disagree with me, but to me, heat dissipation is key