Here is what I've been doing lately and it's been working:
go to google and search "texture" or download a few stock photos
Make a new image
Post your big stock photo on and find a spot you like.
Now duplicate your stock photo and move it around so that your graphic focusses on another part. Change the blending of this new layer to something you like (Sometimes Overlay work, sometimes its Hard Light, maybe a Color Dodge even).
If you want duplicate again, move, and change the layer.
If not, you can either open up another stock photo for move on.
If you want another photo, take a stock and put it on, changing the blending mode to something (I prefer overlay).
Now make a layer and pick some brushes in the color BLACK.
Go abstract with the black, don't overdo it on the brushes.
Change this brushes layer to black.
Make a new layer and fill with WHITE brushes.
When your done, change it to something like Hard Light (Overlay works too)
This is where mine usually looks really good. Slap on text, name it, and go.
When you want a special graphic (say of trees or an angel), use an angel or trees as your stock and use the same method.
Hope it helps.