This will allow you to add an image to the background of all posts by a given user. I've modified the original code to allow for the configuration of background repeats, as well as also apply this style to portal page provided by the SFCore plugin.
Appearance >
Templates > "
extra.less"
Add the following code:
CSS:
.m-background (@mbUserName; @mbID; @mbBackgroundUrl; @mbBackground-size: cover; @mbBackground-position: unset, @mbBackground-repeat: no-repeat) {...