How to change picture representation?

I have been working on my wordpress website for three weeks now and I’m finally getting satisfied with the results. There’s just one thing I can’t figure out.

I’m working in the Gateway theme and I’m making a website for my photography. Now I’m super satisfied with the way my portfolio page looks like (with just using the standard wordpress gallery option, using tiled mosaic as a layout). I like to keep it the way it is now.

The only thing i find super ugly is when you click on my pictures, there appears a black photo album thingy? Which shows my camera settings, room for reacting and the title of my picture (which I can’t change?). I’d actually like it to be more minimal, just the picture in a bigger format with a menu to click through my pictures or something.
Now it looks like this.

http://nikkirulofphotography.com/newborn/#jp-carousel-131

My question is, can I change the way my pictures appear when you click on them without changing the layout of my picture gallery on my page? And HOWWWW?

Oh, I don’t know if I can use plugins, because I’m not using the paid version of wordpress.

Thank you sooo much if you are able to help me!