Before b2evo 7.2.2 upgrade, Horizon Blog Skin had this path to JPG:
images/background-img.jpg
After b2evo 7.2.2 upgrade, Horizon Blog Skin needed this path (which I found by inductive reasoning, going backwards gradually) to JPG:
/skins/horizon_blog_skin/images/background-img.jpg
Note, it has to be a fully qualified path, as above, it can not be a relative path as before the upgrade to b2evo 7.2.2
Additional note: although I have resolved the the path issue, it may indicate that some of the issues, i.e., https://github.com/b2evolution/b2evolution/issues/107 , introduced beginning with 7.x.y may be due to b2evo developers getting confused with paths.
same with 7.2.3