Running qemu-system-mips stable version (tested on 1.2.0, 1.2.50, 1.0.50) with the mips kernel image at
http://wiki.qemu.org/Testing results in just a black screen shown, no messages, no errors, nothing but a black windows appears.
Other qemu-system works perfectly, such as qemu-system-arm, but mips isn't working.
Other images tested (made with OpenWrt, that works correctly in a mips hardware) gave same results.