If you want to use a plug-in lamp you can either disguise the
cord as it goes down from the behind the painting to the outlet or install a
recessed or clock outlet behind the artwork.
If you prefer to have a direct wire light, most of the picture lightstyles are available in direct wire fixtures as well. See the DCF, DT, DSL, DXL styles.
This
DXL24-52 has a satin nickel finish, 24” shade would be perfect for a 35” to 48”
width picture. Direct wire, built in! The graceful swan neck requires quite a bit
of wall above the painting for proportional fit.