To start with, I opened Photoshop and set the paper size to A4 size. I then searched on Google images for a large image of a city at night. I needed a large image so that it wouldn't be pixelated when I started to edit it.
I started with this picture as my background image. I thought it looked mysterious and dark. I then decided my theme would be superheroes/ The Avengers. I started collecting pictures of the various characters and I used the magnetic lasso tool to cut around the parts that I wanted. I then selected the parts I wanted and copied them over to the cityscape which was "layer 1".
I cut around all of these so I just had the figures and pasted them onto the background. I used CTRL+T to alter the size of the images. By holding shift while resizing, it ensured that the resolution stayed good. Once I was happy with the size and positioning of the other layers, I hit enter and they became clearer. The next thing I needed was a title. I searched for a picture of The Avengers title and chose this one.
I couldn't use the magnetic lasso tool for this because it has a light behind and it would bring that too. I used the magic wand tool and selected all the parts I needed and pasted them into the other layers. My finished product looks like this:
All of the layers have been flattened. I did this by right clicking on a layer and selecting "flatten image". This means it is a smoother, smaller file.