Customize where clicking a picture takes you (from the grid)

Hi there, I’m setting up a photography site using the Gridsby theme (which I love btw, thank you) but I have had a couple of people comment about experiencing some frustration after clicking a picture in the grid on my home page.

Their frustration comes from the fact that after clicking an image they will no longer be able to use the back arrow to return to my home page.

Apart from this issue, if the picture is just a picture post that I wanted to add to the gallery (rather than a blog post) clicking it just opens the image up which isn’t that great and once again you can not then back arrow back to the home page.

Am I able to customize what happens when a picture from the grid is clicked.

Ideally I’d like to be able to direct them to a pricing or booking page and always having the back arrow option available would also be good.

Thank you in advance for any suggestions that you can offer.