What are examples of stereotypes in The Elegance of the Hedgehog?

There are certainly some clear stereotypes in the novel. You might be interested in the ones below.

And since it has been written somewhere that concierges are old, ugly, and sour, so has it been branded in fiery letters on the pediment of that same imbecilic firmament that the aforementioned concierges have rather large dithering cats who sleep all day on cushions covered with crocheted cases. 

In Chapter 2, Renee candidly discusses stereotypes. The above quote highlights the stereotypical description of a concierge. With sardonic humor, Renee spends the rest of the chapter reiterating why she fits the stereotype perfectly. She tells us that she is "short, ugly, and plump" and that she has bunions on her feet and terrible breath.
Because of her detached attitude, she has few friends. She admits that she is merely "polite" but "rarely friendly." Here's another example of a stereotype Renee discusses in this chapter:

Similarly, it has been decreed that concierges watch television interminably while their rather large cats doze, and that the entrance to the building must smell of pot-au-feu, cabbage soup, or a country-style cassoulet.

She tells us that she quite happily embodies all the stereotypical traits of the concierge:

I then obligingly flaunt these pauper's victuals . . . because I am a pauper in a house full of rich people and this display nourishes both the consensual cliche and my cat, Leo, who has become rather large by virtue of these meals that should have been mine . . . while I am free—without any olfactory disturbances and without anyone suspecting a thing—to indulge my own culinary proclivities.

It appears that Renee goes to great trouble to create a stereotypical persona that her rich tenants can feel comfortable with. However, there is a reason for her strange behavior. Putting up a facade allows her to indulge her intellectual pursuits and decadent taste for elegant cuisine without recriminations from the wealthy residents in her building. Thus, the stereotypical persona Renee flaunts is actually her attempt at preserving her individuality and personal agency in a class-conscious society.