How to Change the Boot Screen Manually 

Better use the second option because the image you upload should match.

1). Go to C:\Windows\system32
2). Copy ntoskrnl.exe to your Desktop. This is to ensure a backup file.
3). Download and install Resource Hacker.
4). Open the ntoskrnl.exe using Resource Hacker.  
5). Click on "Action" and then on "Replace Bitmap".
6). Save the file as ntoskrnl.exe after replacing the bitmap.  
7). Restart your computer in Safe Mode.
8). Copy the newly created file to the default location.
9). Restart again and enjoy. 

or

The application works by modifying the BOOTMGR system file. Since the application is in beta version and modifies certain critical system files it is always recommended to backup before using it. Though in our testing we found that the application worked well on a Windows 7 x64 SP1 system without any problems.

The following steps cover how to change Windows 7 boot screen:

Step 1:
Download Windows 7 Boot Updater and unzip it.
Step 2:
Run the application and load boot screen file (.bs7). Google it.

 Step 3:
Check that you have loaded correct boot screen using using play. Click ‘Apply’ to to change the boot screen.