It is very easy to place an image of your choosing into a photograph containing a picture frame, thereby replacing what was originally there. If, however, your image has some negative space but no picture frame, it is quite easy to insert one (or more), such as was done here to this beginning image of Andrelica:
This image was given a typical glamour retouch: a bit of skin smoothing, light blue in the eyes and slightly redder lipstick. A mask was then created with Topaz Remask. Everything was masked out except Andrelica and the mesquite table.
I then found a texture for the wall I would be placing behind her. This one is from Mark S. Johnson (http://www.msjphotography.com/), and is called Noise Lab Fabric seamless:
Seamless textures can be tiled together, resulting in bigger texture. This is important, because if I were to stretch a texture using Free Transform to cover an image, the detail in the texture becomes larger. If I am making a wall, then the wall will appear too close to the model. Moreover, large detail in the wall will draw the viewer's eyes away from the model.
If, on the other hand, I Free Transform the texture to a smaller size, then duplicate the layer, move the second texture so that it is next to the first one, and so forth, until I have my wall - then the wall looks more distant. Just remember to have View > Snap checked, and also View > Snap To > Layers checked. Once you have a rectangle of a few textures, you a make them into a single layer via a series of Command-E (PC: Control-E) keystrokes. Then duplicate this bigger texture a couple times, position, and make them into a single layer, and the wall is soon done. I added a Hue/Saturation adjustment layer to darken the wall and slightly change its color to a brown hue.
Now it is time to choose a picture frame or two. Here is a PSD file, containing 33 picture frame layers plus a blue Background layer, from LayerCake (http://www.layercakeelements.com):
With the Move tool, drag the layer containing the frame you want to your image. If you Command-click (PC: Control-click) on the frame you want, Photoshop will highlight the layer containing the frame you chose, making it easy to find. Once you have placed a frame or two onto your image, rotate (if necessary), then resize and position using Free Transform.
Be sure to add a Drop Shadow layer style to your frame layer. This gives the frame depth against the wall. If you have more than one frame layer, you can Option-drag (PC: Alt-drag) a copy of the drop shadow to another frame layer.
Next, drag a flattened version of the image that will go into the frame into your file. It should go, of course, beneath the frame layer, but above the wall layer. Use Free Transform to resize and position. Here is what you might get after vignetting with a Curves adjustment layer and sharpening:
Why stop at just two picture frames? Since this next image has a different perspective than the previous image (even though it was photographed at the same place), this beginning image of Andrelica calls for not only a wall, but also a floor:
Another Mark S. Johnson texture called Puffy Quilt seamless was chosen for the floor:
This was tiled as in the previous example, then given perspective by Edit > Transform > Perspective. Simply hold down the Shift key while pulling out one of the bottom corners to make the front tiles larger. A Hue/Saturation adjustment layer was added to give the floor a dark green cast. I chose green because it is an excellent complement to the red in her dress.
Another Mark S. Johnson texture was chosen for the wall. This one is called Studded Leather 02 seamless. The wall was made the same way as in the previous example, and given a Hue/Saturation adjustment layer to give it the same green color cast as the floor:
Three picture frames were added to this image, and here is the result:
But why stop here? Let's add one more frame and some old wall around the entire image. For this second version, I flattened the image, as it had 17 layers! First, I increased the canvas size on all four sides via Image > Canvas Size... Beneath this flattened layer a Photomorphis texture (http://www.photomorphis.com/store/textures/) from the Ancient Walls collection called Ancient-Walls-09 was placed. A Curves adjustment layer was used to lighten it a little so the Drop Shadow layer style of the picture frame would show up better.
A picture frame was placed on top of the layer stack, given a Drop Shadow layer style, and the entire image sharpened. Here is the final result: