The Collaborative International Dictionary of English v.0.48:

Painterly \Paint"er*ly\ (p[=a]nt"[~e]r*l[y^]), a.
   Like a painter's work. [Obs.] "A painterly glose of a
   visage." --Sir P. Sidney.
   [1913 Webster]

WordNet (r) 3.0 (2006):

painterly
    adj 1: having qualities unique to the art of painting