pictures not showing

I just bought HOT LIGHTBOX, treid it in my joomla website using the already created folder called "images" and it worked fine. But when are created a subfolder under images named "fotos" with pictures it doest not display the pictures.
This is what i wrote on the article:

{photogallery}images/fotos{/photogallery} and it gives me these message

"There are no images in this gallery."

Please where am i wrong. thanks

Maybe you need / at end:

{photogallery}images/fotos/{/photogallery}

Thanks. I resolved it. It does not need a /
I uploaded pictures with the extension for example 1.jpeg and they did not work. But when i changed them to 1.jpg every thing is perfect now. Thanks

Please tell me why pictures with "png" extension do not work at all for me.