Page urls in 5.7 vs 5.4
That is a good question I wish I could answer, because you obviously are an example of how this could be very important. While I don't think there is "a way" built in or an add-on, I suspect there are some that could help with some custom work, if you have a sufficient budget (no idea what sufficient would be in this case). I also know of a developer who some time ago mentioned working on an add-on that I believe would do some of this, but I don't know what became of those plans (and I don't know if image paths were considered or not). I could ask.
Certainly if you have a budget, mentioning it here might help to get attention from potential sources of help. I hope you don't mind me suggestion this.
You should really have a look at the video concerning the new Migration tool for Concrete5.
You can find it here:http://andrewembler.com/2015/11/upgrade-concrete5-sites-57-using-ou...
Really watch the whole thing and you'll understand how page paths and images, or files in general, are not a problem.
In your case, however, you will first need to update your site to a 5.6.x version before you can use the migration tool.