Hint: if you don't have Photoshop, it's worth the free 30-day trial download (in my opinion!) to make this if you are wanting to do something with a bunch of pics all nice and neatly for a print. It's soooooo easy to do and does all of the formatting and hard work for you. Win win!
Here's the steps...I am using Photoshop CC 2015 (which is essentially the same as Photoshop CS 6).
1. Create a folder on your computer and put all of your images that you are wanting to use for your print in there. NUMBER THEM ACCORDINGLY -- when you run the contact sheet option, it puts them in based on numerical order, so make sure you have them labeled correctly in the order you want them (hint: make sure you put 0s in front of your low numbers so it reads it in the correct order!)
2. Open Photoshop, and select File >> Automate >> Contact Sheet 2
3. In the contact sheet option, this is where you need to customize your formatting the way you want. First, make sure under 'Source Images' you select folder, then choose your folder location where your images are housed...and make sure "include subfolders" is unchecked.
4. Next, for the Document dimensions, this is totally up to you. I always do mine bigger (so it's formatted nice and big for printing purposes), so if I wanted a square I would do a 20x20 (inches) or bigger. You can also format in cm or pixels as well. I check "Flatted All Layers" as well so I don't have 52 layers, it's just one (although leave this unchecked if you are wanting to move your layers/images around!). I also make sure I do at least 300 pixels/inch too so it's nice and clear when printing.
5. Lastly, under Thumbnails I tell it how I want my images placed (across or down), check auto-spacing, and then tell it how many columns and rows I'd like. I also make sure to uncheck the option under "Use Filename as Caption" because I don't any captions for my images.
6. When I have my options all selected the way I want, I click OK and let it run! (Hint: this may take a few minutes (and look like what's shown below) depending on how many pictures and how big your image is!)
7. Once your contact sheet is created, voila! It looks like this (or however you chose to format yours!):
8. This is where I like to customize my image a bit...so I create a new Photoshop document (formatting it the same as my contact sheet) and have it have a white background.
9. I then go back to my contact sheet, right (or control on a Mac) click on the contact sheet layer, select "Duplicate Layer", select the destination to be the new document I created, and hit okay.
10. I got to my new sheet, resize (command + T) while holding down shift to retain dimensions, place it where I'd like (with a white border), add text, and BOOM! I'm done!
11. Lastly, I go to File >> Save As, select JPEG as my save option, tell it how big the image needs to be, and BOOM! I'm good to go!
So that's it! Pretty straight-forward, simple, and an easy collage maker if I do say so myself!
I will say to get the formatting exactly right and how you want it, it takes a bit of playing around with creating the contact sheet dimensions, rows/columns, and automatic spacing. But, once you play for a bit you get the hang of it and it's super easy to make! This is totally my go-to collage maker now for more than 9 images and it is sooooo easy to do! Another reason why I love Photoshop.
If you make a collage using this way, I want to see it! Share the link with me in the comments and I'll check it out! :) Hope this is a helpful little tutorial for you!