I would like to put all the images that I use in my application into the same file and access them by key.
Is it possible to use the .strings file for this?
Assuming you mean you want to put the image names, yes it's possible.
In your code, just use things like [UIImage imageNamed:NSLocalizedString(key, @"")];
Where key is the key that points to the name of your image. Then in the .strings files, point to the right image file based on the locale.