"On" indicates the surface where the painting is displayed. "In" would suggest inside something, "at" would indicate a general location, and "by" would suggest proximity but not necessarily placement on a surface.
The painting was displayed prominently on the gallery wall. / ഗാലറിയുടെ ചുമരിൽ പ്രാധാന്യത്തോടെയാണ് ചിത്രം പ്രദർശിപ്പിച്ചത്.
