Hey
Minimal effort solution would be:
1. Prepare a 624x244 24-bit JPG splash image, GIMP probably works.
2. Unpack TNOSSPLASHFORM_F.dfm delphi form from EWSF.EWS using Resource Hacker.
3. Replace hex data between brackets in Picture.Data section of Image1 with hex encoded string of your new splash jpg, prefixing it with 544A504547496D616765F1390000 (the .dfm is a text file).
4. Replace the resource in EWSF.EWS, again with Resource Hacker.
I didn't test this, so let me know if it worked.
Edit: tested today & it works
If you want more customisation you can also write your own dll with compatible api and entirely replace the original.