"a shady operation"

"a louche nightclub"
"a louche painting"

"there was something fishy about the accident"
"up to some funny business"
"some definitely queer goings-on"
"a shady deal"
"her motives were suspect"
"suspicious behavior"

"the shady side of the street"
"the surface of the pond is dark and shadowed"
"we sat on rocks in a shadowy cove"
"cool umbrageous woodlands"