Can you take 2 different pictures and put them together?
The easiest and most common way to put 2 photos together is a collage. Creating one is an effective way to showcase multiple related photos without posting them all separately.
How do I compare two image resolutions?
Try WinMerge which is a free software to compare files and images and check differences between them. You can compare not two but three images at once using this great free software. It shows and highlights the differences between the images. If you want, you can also use a free online tool to compare two images.