How can I create a collage of over 2000 photos?

You could use an image editor like Photoshop or Gimp and create a large canvas and adding all the images as layers. Or something like Illustrator and Inkscape, that allow you to treat the images as object, for a bit more freedom to play.

But honestly, I think that 2300 photos on the same image are going to be huge, and I'm not sure if it's manageable with conventional tools. Of course it depends on the resolution of each photo.

Since you said this would just be a background then you might want to try 'googling' the words: photo mosaic maker. You'll find lots of software and online applications to make a large photo mosaic. 'Mosaic' seems to be the word that the app developers prefer for this type of activity. We'd be interested in your result after you finish.

You can use ImageMagick (open source and cross-platform) and use the command (assuming that your photos are PNGs):

montage *.png -tile 1x -mode Concatenate out.jpg

• -tile 1x: concatenate vertically (use -tile x1 for horizontal)
• -mode Concatenate: concatenate without any white space between the images

More details on the montage program (part of ImageMagick) if interested.

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Some ImageMagick useful commands for pre-processing your photos before the collage:

• you can resize the image (to approximately 2MB in this example) using:

  mogrify -define jpeg:extent=2048KB out.jpg

• you can modify the dimension of a bunch of images using (to 30% in this example):

  mogrify -resize 30x30% *.png

Also note that JPEG/JFIF supports a maximum image size of 65535×65535 pixels, while the PNG specification doesn't appear to place any limits on the width and height of an image; these are 4 byte unsigned integers, which could be up to 4294967295 .

and if you are curious: Why does ImageMagick's montage limit the JPG output to 65500 instead of 65535?

A couple of ideas. If you happen to be a Lightroom user, then I believe you could do this with the Lightroom Print module - you'd set it up as you want, with the size, settings etc, then export it as a file rather than actually printing it. I've done this with smaller sets of images (e.g. for a triptych), but I don't see any reason you couldn't do it with a large set like this, so long as you first put all the images you want to use into a single Lightroom Collection.

Also, I've made image collages as slides in PowerPoint, using as many as 20 or more images on a single slide, with overlaid images, angled images etc. I expect any slide you produce in PPT could then be exported as a jpg to use in some other program (though I haven't actually tried that). I've only done this as part of a PPT slide show, so I can't be sure how it would work for other purposes, but it should be experiment, using just a few images to start with. One thing I've noticed is that PPT creates very large files, so you'd probably want to be sure you're working from the smallest versions of the images that you can get away with using, before you begin.

InDesign or any other Desktop Publishing Software.

• Choose a suitable view-quality setting. This won't affect the results but will not draw the images in a high-resolution while you are editing the document. Once you export, they will be used in the high resolution.
• Create a canvas with the desired target size.
• Add placement boxes in the shape that you want.
• Using Adobe-Bridge (or Mini-Bridge panel in InDesign), select all the images that you want to add to the image.
• Click on all the placement boxes in the desired order.

Downside: You are manually adding 2300 boxes and placing images in them. However, it should work with these many images, and you have all the flexibility you'd want.

I am not sure if you are refering to a mosaic software, not collage one. https://www.google.com.mx/search?q=mosaic+software

I would do some previouis steps.

1) Make a backup of my photos.

2) Use a batch resampling and croping of the photos. I would need to calculate the size of each one but let's say 500x500px will do.

3) Use a mosaic program.