Picture a large assortment of framed pictures on an end table. A large collection of mismatched picture frames on a table top or shelf can look like clutter. Plus, it becomes time intensive to dust the frames and the table top!
First: To save time dusting, hang photos on walls rather than place them on tables. This will free up horizontal surface area and simplify dusting.
Second: Buy large inexpensive almost poster-size picture frames and print out your favorite pictures and make photo collages. Chain retail craft stores often sell many large frame options that are reasonably priced. A little acid-free double sided photo tape works well to hold them in place on the mat. I usually choose a mat (large piece of colored paper), again from the craft store, that goes with the colors in the room where I plan to hang it.
I can also cut and trim each photo as needed to fit even more together. I can group photos together and display over 30 awesome pictures in one simple frame on the wall. Brighten and personalize a laundry area or back hallway with a friendly photo collage.
Third: To reduce the visual clutter of multiple mismatched picture frames, stick with buying only one color of frame (black or white usually is easiest to find and be consistent). This draws the attention to the pictures rather than to their frames, and it ties the pictures together better as a grouping.
Keep in mind that the ideas suggested here are not geared toward preserving photos for posterity. That would require archival quality acid-free materials. These suggestions are given to simplify displaying and enjoying the photos you have today!