1) You would need a program to edit .exe files i.e. Resource Hacker: http://www.angusj.com/resourcehacker/
2) Find the image you want to change and export the image.
- Export image
3) Edit the image
4) Replace the image using the Resource Hacker program.
- Replace image
5) Do that for all the images you want to edit
6) Save the file. Make sure to have a backup of the original .exe file.
Here are some of the pics of the exe file I edited.
Before pics: