Your goal is to create a visual triangle.
Start with something large to use as an anchor to center, such as a mirror, or a large piece of art. You could even use a wreath or large tobacco basket.
Layer artwork and/or photos of varying heights in front of your piece, creating the “triangle” with the most high point being the top of the large center object and the artwork or photos on the sides moving downward. The pieces should have similar weight to fill out the triangle.
Add in some accessories of various heights and move things around until everything looks balanced and to scale.
Have fun tweaking! Using items with various heights and textures will make it look interesting!