First, catch your rabbit -- that is, get a decent digital pic to play with. Here is a photo of me on the deck outside Isabel's window, with the back woods, in all their drought-given brownness, and the playhouse behind me. Crop the photo at some time during the process to just the area you want. It doesn't matter when you do this, but if it's a big picture and you do it first, other processes will be a bit speedier.
In the LAYERS menu, make a duplicate layer. This will show in the layers list as a duplicate of the background layer, above it in the list. This is the layer you work in; you leave the original layer alone.
In the FILTERS menu, choose Blur, and then Gaussian Blur. Use the slider to make it more or less blurry.
Then go back to the LAYERS menu and choose Add Layer Mask, selecting Reveal All.
Then comes the magic part. You choose black as the foreground color, and get a big soft-edged brush, and PAINT over everywhere that you want to see through the blurry mask layer to the original photo below. In this instance, I used a normal paintbrush to reveal my face and front and the pendant. Then I used the options panel for the brush to choose Dissolve, not that I had any idea what would happen, and with a brush with only 12% opacity and the Dissolve characteristic, I painted over the rest, and got all those little sort of sunflecks. Finally you merge layers, and lower the image size if you want, and it's done.
I can't wait to try this with a closeup of a jewelry piece, and to explore all those other options - other filters, other brushes -- WHEE!