There is one nice full-colour illustration in the Cityscape D&D sourcebook that I'd take as primary inspiration, but illustrations are hard to come by. There are a few illustrations (black and white line art) in the sourcebook The Complete Book of Elves, which are of the cities of the Grey Elves, the 2nd edition analogues to 3rd edition's Sun Elves. There are also descriptions in the Forgotten Realms novels of elven cities like Cormanthor, which are in a style I'd like, notably in Elminster In Myth Drannor.
Edit: Actually, it turns out I had already saved a copy of the Cityscape illustration in my reference folder, so here it is:
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And here's the B&W line art one from the Complete Book. This one shows some exterior and interior architecture, some furniture, and a typical pet.
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