LONDON — People lining up at a ticket booth under a Ferris wheel. Police officers questioning a skeleton figure as his dog looks on. Two new Banksys have popped up at the Barbican Center here, authenticated on Sunday by the British graffiti artist on his Instagram account.

The pieces, which refer to the work of the American artist Jean-Michel Basquiat, appear to herald the start of a major exhibition of Basquiat’s work, opening on Thursday at the Barbican Center.