I think virtually all boot ROMs will be specific to if not a specific model of NIC a specific family as the ROM needs to include a driver for whatever ethernet chip its working with.
From what I've read the Intel EtherExpress 16 cards have, by default, an old-style IPX ROM that's only capable of booting from a NetWare server or something that looks 100% identical to a NetWare server like Mars NWE - the ROM will include a mini NetWare client that will try to attach to the nearest NetWare server and mount SYS:\LOGIN\NET$DOS.SYS (a floppy disk image with an odd choice of extension) as A: then continue the boot process from there.
There is newer Novell RPL ROM ("Novell NetWare Ready Firmware") for these cards which should also support booting from Windows NT. When booting from a NetWare server these newer Novell RPL ROMs can present a list of disk images to choose from which is kind of neat:

There is also an RPL implementation for Linux and it can apparently be made to work with Mars NWE as well as chain load iPXE from a NetWare RPL boot ROM though I've not tried doing either - I've only pointed RPL ROMs at real NetWare servers so far.
While a bit off topic, if the goal is iPXE then any card with at least a Novell RPL boot ROM will probably do the job.