I'm giving only one layer style to my MS: it is standard drop shadow.



I don't really like grayscale color gamma (personal) so I will color balance the whole image a little bit.



And now the final step.

Switch to pen tool and make a curve like so.







Now stroke the whole path using Stroke Path option.



Here is the brush with witch I've stroked the path.



As all this curved thing is on the separate layer I will style this one too.