Thank you Ted, nice to see some extra details filled in!
I hadn't realise this picture also appears in 'Suitable for Framing' - makes me think it's more likely to be just re-using a prop rather than anything more deliberate, but who knows?
Impressive attention to detail that they went to the length of signing a prop picture with the name of the artist character. On the other hand, I remember in that scene in 'Suitable for Framing' that Dale Kingston says something like "No matter how abstract the painting, he always signs his name realistically". I'd somehow never interpreted this comment as referring to Sam Franklin personally, but perhaps this is how it was intended. Maybe even at one stage they meant to give more prominence to Franklin's paintings in this episode, hence the signature being written in that way?
Franklin's repertoire seems somewhat diverse. This painting is fairly abstract, but elsewhere the episode we see him painting (presumably) a nude portrait, and when he arrives at the art viewing Kingston says something patronising like "You're the painter of these arid landscapes". It seems Franklin hasn't quite found his style and so can't break past the hospital market.
To change the topic about noticing other things in other shows -- in "The Most Crucial Game," after Dean Stockwell's character is killed and they are at his house, the music from "Etude in Black," is playing in the background. Then it fades out when the bug static takes effect.