They mostly have stacks of books laid out, with the artist drooping rather plaintively behind them.
We've been around on this one several times. Here's how it breaks down:
Robert: "Drooping plaintively" evokes a sense of pleading (for customers), along with helplessness.
Laura: "Drooping wistfully" better conveys yearning tinged with melancholy (over the lack of customers)
Our friend (and Robert's editor) Elizabeth: "Drooping languidly"--lacking in vim or energy or
"drooping torpidly"--having lost motion or the power of exertion or feeling, sluggish in functioning or acting.
Neither of the ones I like have that beseeching quality you're looking for, but they add to the general tone of ennui you're evoking.
So far, we've invested a rather impressive amount of brain power into choosing one word.