Overlay image for watermark
 

What is the ideal size for the overlay image for watermarking?
I assume from reading through posts on this forum that the file format to use is .png. I just want to know what the best size to use (height and width) and does it need to have a transparent background?
Thank you

That would all depend on the normal size images you upload. The good thing about the overlay it does not destroy images so you can try out different images and see what works best for you like try 250-300 x 50 and go from there and use what looks best to you.