Thanks for the tip. I'm using 4.x. I tried "*/; *.jpg; *.png" and it is copying the entire subfolders over rather than just the jpg and png files located inside those nested folders. I believe since the directory mask */ is specified, it's just copying over the whole directory over.
How do I make it so it goings through those nested directories but only copies jpg and png files only in those directories?
Depends on version of WinSCP you are using.
With 4.x, you need to use: */; *.jpg; *.png
With 5.x beta, it is enough to use: *.jpg; *.png
Also with 5.x you can use file mask editor: