SteamProfilePreviewer автор Miko

This extension enables you to preview the items in the steam points shop on your profile. This way you can decide which fit your profile best before buying anything.

When pressing "Preview" on one of the items, it will be displayed in a menu on the right side. Then, with a press on the menu's preview button, your profile will be opened with all selected items applied to it.

Instead of logging in, you can enter a link to the profile that the items should be previewed on in the field below the preview button.
You could even "beautify" your friends profile and send them a screenshot of it!

Currently supported items include:

• Animated, static and tiled backgrounds
• Avatar pictures
• Avatar borders
• Mini profile backgrounds
• Items from Game Profiles, also selected individually

PS:
When Steam changes their websites, the extension might break.
I will respond fastest if you contact me per mail.
Thanks for letting me know about any issues!