The logo/image displayed during a call in progress, Call History, etc... can be changed in your phone's registry. You need a registry editor to access the phone's registry. Just do a search on the internet for "Mobile Registry Editors". Most of them are free-ware.
If you want that logo to be the same for all screens, you can change the image itself instead of making the registry changes. Your phone needs to be application unlocked. In the Windows directory on your phone you'll find a file called: ms_mobile.gif
By replacing this image, and soft resetting your phone, you've changed most of the screen's logos/display images.
If you want a different logo for different screens, you can use the registry editor to manually set them. Go to:
under the sub-tree you'll find all the screens (MSCdial, MSBranding, ...)
Almost every image can be changed here.