Just a tip on how to convert your current selection to a shape that also can be used in future as vector format.
Take the selection with your favorite method.
In my case i use the magic wand tool
After you took the selection go to path palette and press the little arrow on the top right corner, then select the “make work path”
enter the tolerance value 0.5, why..? because we want to maintain the original selection as much as possible…Note here that the value less than 0.5 is not acceptable.
Now your work path should be created..
Now go to the Edit menu and select “Define Custom shape”
Enter the name of desired shape and press OK
Now this shape is available under the Custom Shapes.
Just use it in the way you want and enjoy.