Where in the php code would a background image on the home page be managed?

[schoolboy]

Of course some answers may go down the line of yes can do, but why would you want to? Which shouldn't be too difficult to answer, but from the askers perspective may be seen as a path that could cause trouble.

That's well said... My "observations" are sometimes misconstrued as criticism, or "arrogance" - and for that I can only offer apologies. With 12 years' experience in Zencart, and almost 20 in eCommerce (particularly the marketing side) I have often learned the hard way - usually because I put MY personal "wishes" ahead of what is "sensible".

Today, there are some 120 million "online retailers" around the world - all competing for eyeballs - and the principal harvester of eyeballs are the search engines. So... with quite a few million competitors - all battling to get eyeballs, I take the view that by following and incorporating the protocols of the "industry" (aka worldwideweb), I put my sites in a better position to get eyeballs than my competitors.

Right now, AMP (Accelerated Mobile Pages) is all the rage - and Google (I hate them as much as anyone) is really pushing this format. So... I am now looking at how to incorporate AMP into my zencart frameworks. If I get there before my competitors, I have an advantage in better ranking on search results - and therefore a better BUSINESS advantage. And that's what really matters... I want to "out-business" my competitors.

I care not a hoot about the "shade of green" I use on the website background if I am selling well and making profits - unless of course it can be proven that my choice of green is somehow causing people not to buy stuff.

Lean and mean sites will dominate the WWW soon... Mobile usage is dictating that, and Google is a follower, just like the rest of us.