There may be an option to skip some checks.
Some BIOSes have options like "fast boot" or similar which will skip memory checking and save few seconds of boot time.
Another point would be to see which video card is set as default. I've seen many BIOSes which are set to by default try to boot a PCI video card, but the system's main video card is PCI-E. That could save few seconds too.
Another thing would be network boot ROMs which can take few seconds top load and would not be needed since the computer boots form local drive.
Yet another thing to add to the disable list would be RAID support, if it's not needed and support for extra disk controllers. Many motherboards have additional drive controllers which may not need to be used if there are few drives. It may be needed to physically reconnect drives to the ports provided by the controller on the chipset. After that, the controller can be disabled and that may save some boot time.
One more thing that might make an impact would be to disable floppy drive in BIOS, if the computer doesn't have one. Some newer motherboards may not even have floppy support anymore, but a significant number of those I've seen which do, have floppy set to standard 1.44 floppy in BIOS and are set not to show errors if there isn't one connected. That might save some time during boot.
Sometimes SATA and PATA drives may need some time to initialize and that time can depend on the port the drive is connected to. So it may be smart idea to disconnect all drives and see how much time it takes for BIOS to show that it can't find any bootable devices. If there is a significant difference, then it may be a good idea to try experimenting with connecting drives to different ports on the motherboard (but make sure only ports provided by the integrated drive controller are used!). I've seen cases where a HDD could take as much as 30 seconds to "initialize" on one port and only take a couple on another.