This is a really difficult question to answer because the only real answer is that it should be done in a way that looks good for the purpose. This is so obvious it seems condescending.
Programmers have a term for a process that they use to help themselves find the flaws in their program logic: Rubber Ducking. Essentially, they explain out loud to a rubber duck line by line what they are doing and why and this helps to clarify problems they aren't able to see.
So what might be helpful to you is to have a dialog with yourself: what am I trying to show with these photos? Who is in them that must be shown? Do any have compelling visual interest or composition? If I scatter them on the floor is this better than if I pin them up on the wall? If I pin them up on the wall and take a photo of them, is this too hip, too hippie or too hipster? If I collage this is it too casual? If I grid it is it too suit-and-tie? If i juxtapose a photo of a cow, a pig, and the principal will I receive my diploma?
Really the point of design and art in general is to eliminate possibilities.