Wallpaper Picker Image Choices Don't Scale Well

When enabling fractional scaling, the images displayed in the Background section fail to scale properly. They are unexpectedly large and take up greater amounts of space making it more difficult to scroll through the choices. This happened in my testing for 1.25x scale.

Expected:

Actual:

Steps to reproduce:

1. Open GNOME Settings
2. Set Fractional Scaling Preference to 1.25x (just an example)
3. Navigate to Background section to observe the out-of-proportion image sizes