Since Nov, 2013 LLX has supported the use of 9 patch images as backgrounds for icons, folders and panels.

A 9 patch is simply a special .png graphic with stretchable area(s), defined by 1 pixel black lines. It will be automatically resized to contain anything from nothing at all, all the way up to an entire panel or folder window.

More info

http://developer.android.com/guide/topics/graphics/2d-graphics.html#nine-patch

You can use Photoshop to create or edit a 9 patch image, but these must then be compiled for use in LLX.

9 Patch Editor (in the Play Store) can save your image in a compiled form.

https://play.google.com/store/apps/details?id=me.denley.android.ninepatch

Once you have the compiled 9 patch image somewhere on your device, just select Customize for your icon, panel or folder, and under the Box tab, tap Normal background image and select the file. You can use the same or different file for Selected background image so for instance an icon “button” can appear to be pushed in when tapped.

Some I have collected to get you started  (zip archive)

https://app.box.com/s/0rs5818i7g7wamlrrqho

These are not compiled!