Little tutorial for those who can't get this working:
At the end, you wanna have an HDLoader.ELF hable to boot on the Memcard in the DMS dev1 mode and patched to support 127Go+ HDDs.

1/ you start with the original uncompressed HDLoader.ELF
2/ you patch it with the hdlpatch_0.2c.zip using the "hdlpatch_0.2c /N /C /S /B /F /L HDLoader.ELF HDLoaderpatched.ELF " command.
3/ you unrar "BMP BATCH-DMS-Devolution-1-Tested.rar"
4/ you copy the HDLoaderpatched.ELF in the unrared folder and rename it to HDLoader.ELF
5/ you run BMP-BATCH.bat
6/ finally you get your CustomHDLoader.ELF with a nice background which is what you wanted!