VESA vbe is not an option on non-x86 architectures jggimi, as described in
FAQ 11.2.10 there are two ways of getting X on macppc.. the unaccelerated framebuffer (..
wsfb(4)) or the accelerated X drivers like xf86-video-ati (..and maybe nv).
If you use the unaccelerated framebuffer you'll be stuck in 8bpp mode at a resolution controlled by the Mac firmware.. it cannot changed after the kernel takes over.
@Mr-Biscuit, please read
/usr/X11R6/README.