Now for the last heart.  Notice that the image I want to use has a heart background on the kittens?  Here is a good way to have this go well.

Make your heart layer active.  Click on the background with the magic wand.  Go to Selections.  Modify/Expand by 5 pixels.  Invert the Selection.  Add a new layer.  Copy the kitty heart.  Paste Into Selection.

Go back to the heart layer.  Click on the background with the wand.  Expand the selection by 1 pixel.  Add a new layer named red.  Flood fill this with a choice of red you like in the image.  Move this layer under the kittens.

Make the kitty image layer active again.  With the magic wand, click on the red around the kittens and delete it.  Clean up any white border with the Freehand select.

Once that is done, click on the kitty background with the wand.  Expand the selection by 2 pixels.  Gaussian blur by 1.  Now your kitty image is perfectly blended.  Move the heart layer above the image layer.  For the final image, I left this one as a jpg and made a textured pink background.