Key word in the OP's post: FREE. GraphicRiver is not free. Also for web-dev PSD templates it'd be ThemeForest, not GraphicRiver
Either way though they only give 1 free file away a month, and it's usually on a personal license. You cant use any items from the Envato marketplace for commercial/re-sale unless you buy an extended license which is usually in the mid to high $xxx range.
For completely free ones WITH commercial rights you'll be very hard pushed. Nobody is going to allow you to sell the thing they are giving away for free, and rightly so. You'll need to pay like everyone else, or learn to do it yourself
There is not really too many easily acquired (there is some I'm sure if you feel like digging) commercially available designs in PSD format worth getting that are publicly offered for free (paying for a membership to a place that gives you free slices is not free) unless you make them yourself, and at that your time isn't free so...you either should consider paying a little upfront for legit commercial use and have a selection to pick from at a site with a wide variety or go hard and learn photoshop.
Option 2 (opinion here) will always be better unless you have the money and can convey exactly what you want to your designer and this based on paying for something and getting it once is final, paying with time to learn to do it yourself provides reproducible results.
Again I am sure they are out there...but not many people that are aware of quality free to use commercial skins are going to be quick to share them so others can make money off the same skeleton as them making their "design" worn and to played out.