Yes, I do know that the best accompaniment is a guy with guitar/bouzouki/etc sitting near you. But there are cases when you don’t have a guy of that sort
When I’m bored of playing alone or with a metronome, I usually take a midi made from some ABC with gutar chords from AbcExplorer and remove the melody line. Then you have very simple piano accompaniment - better than metronome, but still not too much.
It’s not an “easy” way to do it, but here’s how I generate accompaniment for myself:
First, I use a program called Harmony Assistant, which is basically a program that lets you write and play sheet music. To go with it, I got a program called RealGuitar, which takes input from a midi port and generates guitar backing. Then I got a program called LoopBE to create a virtual midi port, and directed Harmony Assistant’s output to that midi port. RealGuitar takes Harmony Assistant’s input and generates guitar backing. Voila!