Basically, ssLauncher uses the system wallpaper, but also supports to set different backgrounds for individual pages. There are two approaches to do this:
1. The following screen will be shown by menu > theme > background images.
In the screen, you can set the backgrounds for EACH PAGE TYPES: cover page, app drawer, app group... Additionally, the backgrounds for popup menu, dock menu bar or parcel view can be changed in here.
The important is that this settings will be saved into theme. That is, it can be shared with your friend by menu > theme > save theme.
2. You can set page backgrounds for EACH PAGES in the menu screen (see the below).
If you are using auto orientations (portrait and landscape), check the option 'different background' in menu > preferences. This page background has higher priority than the above mensioned (in 1) and will not saved into theme but the page properties.
* Tip: When selecting an image, try to hold the image. Then you can crop the image.
** Turning off the system wallpaper:
You can turn off the system wallpaper in menu > theme > margins and others.
*** Layers of background:
The system wallpaper is the bottom layer and the page background is above it. Therefore, if you have set transparent image as a page background and the system wallpaper is on, you could see the system wallpaper through the page background.
**** Page background is not drawn while page transition:
When you are using some animations such as 'Sliding' and the system wallpaper is turned on, the page backgrounds will not be drawn while page transition for the higher performance. This could give you very bad experience if the page background has been a fully opaque image.
In this case, I recommend you to turn off the system wallpaper OR change the animation type in menu > theme > animation.