Unfortunately this is not a perfect world and there, as always, some restrictions that you should be aware of.
MILO is not meant to load operating systems other than Linux, although it can load images linked to run at the same place in memory as Linux (which is 0xFFFFFC0000310000). This is how the flash management utilities can be run.
The PALcode sources included in miniboot/palcode/blah are correct, however there are problems when they are built using the latest gas. They do build if you use the ancient a.out gas that's supplied in the Alpha Evaluation Board toolset (and that's how they were built). I'm trying to get someone to fix the new gas. Meanwhile, as a workaround, I have provided pre-built PALcode for the supported boards and David Mosberger-Tang has a fixed gas on his ftp site.