A way to make museums a little more useful?
I'm not exactly sure how this would be done, but my main thought is being able to level up certain skills while there. This wouldn't be like the Art Centers, but I find the only real purpose of Museums in the Sims is to go there for an Art related aspiration or as a want. You go there for a minute or two and you leave. There often is little use to visiting one just to use the one easel since it often is already taken by some other Sim. My main thought on making them a bit more useful is having a Guide there (like how you will encounter mentors in some places.) You could interact with them and they will give you some skill from talking about art. Also, if you end up talking to an Art Lover, you could learn a little from them.
This could affect the painting skill (of course) if they talk about paintings and the handiness skill if they talk about sculptures. (Maybe even some logic skill, since some artwork and sculptures actually do rely on math and diagrams.) If you have Jungle Adventure, you could also gain skill in Selvadoradaian Culture and/or archeology if a museum has artifacts from the pack. If you have Vampires and there is art of Vampires or the gargoyle statues you could gain skill on Vampire Lore. If you have Get Famous you could probably gain Acting or Media Production skills - if you consider the concept of the Guide supplying information of a techniques that were used on the set, what sort of acting method an actor used to get into character and the like.
I wouldn't expect the skill gain to go up fast doing this, but it would make going to a museum and socializing there a bit more useful to a player who is working on the forementioned skills while helping build up their charisma skill as well. Because really... I practically never visit museums in the game.