I haven't checked to see which are PS2 and which are PS3, and I can't guarantee that no extensions have been used, but there is a PowerGallery sites thread which may provide a part of what your looking for.
Powerstore functionality is ready to go, with settings particular to your site being defined during the easy visual set-up process.
The limits to design customisation are dictated by your imagination and CSS skills. Being template based, you can propagate your design ideas site-wide by adjusting the templates (apart from one or two pages). Branding your site with site colours, logos and graphics is fairly staight forward. More extreme modifications require a good understanding of CSS (or asking questions here!).