How to customize the Hexen STARTUP lump (SLADE)?

[ETTiNGRiNDER]

That is, the loading screen with the big HEXEN logo and the two skulls that join up with vertebrae at the bottom while loading.  The ZDoom wiki gives some explanation of the format and says that SLADE can be used to replace these, but while SLADE can certainly view the graphic, I don't see an option to make one on the image conversion menu (I have v3.1.1.5).  Where's the option for that?  Or is the wiki wrong in implying there is one?

[scifista42]

Go to "Edit -> Preferences -> Graphics" and check "Offer additional conversion options", then the format selection box in "Graphic -> Convert to" will let you choose "Planar (Paletted)" if the lump's name is "STARTUP".

[Kappes Buur]

That sort of startup sequence was utilized in two pwads :

Enjay's GENE-TECH and Tormentor's Blade of Agony (still in development).

 

I looked at both of them and I have no clue about how they did it.