Make a single image from multiple images by collaging, overlaying or assembling an array of image components.
Into a Collage...
Make a collage from a collection of images:
Assign relative weights to the images:
Overlay an image with a second image:
If the background of the overlaid image is not transparent, it will obscure the image below. Use the option setting Background->None with Graphics and Rasterize to make images with transparent backgrounds.