Is that *art* also limited to 4 colors?
Actually, it's limited to a single color. In other words you can use pen 3 (I think?) and pen 0, which is your background color.
As far as I know, the old 1.x loadwb only supports 4 pens (colors). To get more, you'd have to ditch loadwb and run a different workbench. But I don't think there were any (besides maybe one for a custom graphics card) that were for the 1.x roms. So, basically, you're screwed.
And I understand I can't use png icons, but I've got a program IconMagic or something. I think I can make WB icons with it...
Probably. Just remember workbench 1.x can only use the first 4 pens. The defaults are (pens 0-3)
blue(clear)/white/black/orange, IIRC.
And can I adapt the font of the title bar / menu and the one under the icons?
Yeah, you can change the default pens and fonts with the "Preferences" program, I believe. (The fonts may need a custom program, which should also be on aminet)
EDIT: upon reading Piru's post (which wasn't here a second ago!) I agree. The default program only allowed Topaz 8 or Topaz 9. I still think that there was a hack to allow others, though. Scour Aminet. In the really old stuff. ;-)