These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
The scene with Dot powdering herself is a recreation of Seurat's painting "Jeune femme se poudrant". Dot later refers to it as "her" painting and Georges mentions he has repainted it with another model (which, particularly with the original production, explains why Dot looks nothing like the figure in the painting).
If recalled correctly, the Celestes were gossiping that "George has another woman." This leaves room for the audience to infer that George is with Madeline Knoblock, his real life mistress, (and painted her over Dot's painting).
There are numerous references to visiting the follies, which would be the subject of Seurat's later painting "Le Chahut".
The painting "Une Baignade, Asnieres" makes a brief appearance (just before the song "No Life"). It's not entirely clear from context, but the idea is that the action of the painting is taking place on the bank of the Seine opposite to La Grande Jatte, since many art critics believe that's where it was painted.
George's laser machines are named "Chromolumes" after a phrase in one of Seurat's personal letters, in which he described himself as a "chromo-luminarist". Another subtler reference might be that modern day George, like his ancestor, thinks of himself as both a scientist and an artist (he describes himself as "an inventor-sculptor").