With Windows 7 explorer managing and customizing folders is easier than ever before. Applying or adding a new picture to a folder (folder picture) is very simple.
Step 1: Right-click on the folder that you would like to customize and click Properties option.
Step 2: Switch to the Customize tab.
Step 3: Under Customize tab, under folder pictures section, click on Choose File button and browse to the image file that you want to set as folder picture for the current folder.
Step 4: Once you are done with your custom folder picture, click Apply button to save the selected image as folder picture for the current folder.
Step 5: Done!