Imagining a layout for your art can be difficult. Here is a quick hack to eliminate the guess work:
The best way to organize a gallery wall is to cut out sheets of paper in the size of your prints and organize them on the wall. You can use kraft paper, newspaper, anything large enough. Once you have the sizes all cut out, tape them onto the wall with painters tape. It’s important to use painters tape as it won’t peel your paint, and you can easily remove and rearrange. Once you have your final layout, mark the sheets with what image will go where, and take a photo of it so you remember where to hang everything.