An ekphrasis [3] is a poem about, describing, or inspired by, a piece of art. Rather than writing a poem based on a piece of art, try writing a poem inspired by an existing ekphrasis.

An ekphrasis [3] is a poem about, describing, or inspired by, a piece of art. Rather than writing a poem based on a piece of art, try writing a poem inspired by an existing ekphrasis.
Links:
[1] http://www.pw.org/writing-prompts-exercises
[2] http://www.pw.org/users/writing_prompter
[3] http://www.poetryfoundation.org/learning/glossary-term/Ekphrasis