If you are in an upscale retail area, you'd better match the look or you will be made to match the look, one way or another. That Weill Brothers painting of the shop I remember. I've been told it was tinier than it looked and very plain inside. You had to be specially invited into the back office where the rarities and better items were.
Here it is today, an antique shop as is typical of the block:

The whole side of the block have nothing remotely flashy in the windows, no big banners. They're saying, "Tourists, if you're not here for a reason, keep walking."
Blowup stamp pics are great, but you still need to change up the window to keep from people getting too used to what they see every time they pass. I remember a dealer who sold those brass US stamp pins; they were a fair part of his window display. He said it was great for meeting women who came in for them, but anyone who bought or sold actual stamps from that group was really, really rare. Treasure Coast may have the best idea: name in large letters on the window and stamp blowups so someone calling them or responding to ads can find the shop easily.
As for smash-and-grab, jewelers put real stuff in their windows and remove them at night. I wouldn't do that with stamps just because of fading. It's a similar long-term problem with normal interior fluorescent lights. Color copies work, but what kind of response would a dealer get when the item in the color copy has been sold? There's a lot of work for updating that kind of display. Color copies of packets, then.