Hi,
These floppy images are failing because they spin waiting for a keypress with irqs disabled, and SeaBIOS doesn't enable irqs in the handlers being called (same issue seen on "d090723b.zip" image reported by Roy).
I've put a test image with a workaround for the issue at:
http://linuxtogo.org/~kevin/SeaBIOS/test/bios.bin-0.5.1-debug-20100311
See below for the patch I used - I'm still researching it, but the image can be used for testing.
I tested only with NeXTStep 3.3 booting from hard disk and it worked.
I'll test the rest today but considering the PS/2 mouse emulation is not working (there is a bug in it that prevents NeXTStep PS/2 mouse driver and old X11 PS/2 mouse drivers working).
But for now, it boots up to the GUI flawlessly.