Keep it up mate, I too am trying to do similar things. I have made edited team logos for all the teams in ICC2005.
You can download them as a zip in this thread at cricketweb
http://forum.cricketweb.net/showthread.php?t=14592
I was also looking at updating the background pictures. You are right, they are old and grainy and 8bit colour, when the game will take much better quality pics despite running at 800x600.
My problem is finding really good high quality photos of cricket grounds. Google image searches don't come to much and then best images have to be about 1028x768 or more to be shrunk down to make a good background. There are places like gettyimages, and they have extensive archives but you need to register and pay for them.
Because I could only get low res pictures, I had to resort to stylising them in photoshop to hide the lack of detail. However I did find a few good "big" pics.
So, I kinda figured it was an impossible job to get them all updated. However, I did do a few. I will find them and upload them for you.