I know what you mean by the use of models to highlight the clothes. I see perfectly ordinary pieces made to look spectacular through styling. I also think that models are helpful in giving the store a particular attitude or style. Many of the stores I see use edgy models with piercings and modern haircuts, for example, to lend their pieces a bit of edge.
At the same time, like you say, I'm not sure that models are necessary. Well lit photos can be adequate. And the use of props or lighting can help give the store an atmosphere as well.
Thanks for the list of eBay stores. I'm looking more at Etsy myself, but it'll be great to reference those eBay stores for ideas.
I have a few books that I came across that might be helpful. I haven't finished reading them yet, so I can't vouch for them. There's Antique and Vintage Fashions by Barbara Johnson, The Little Guide to Vintage Shopping by Melody Fortier, and Virtual Vintage by Linda Lindroth and Deborah Tornello. What I can say so far is that the first one is a good reference for changing trends that might help you date the vintage. Each year has a list of the trends that became popular that year. Virtual Vintage is a bit dated in the "basics" section that I've just started, but the other sections seem helpful.