I have never seen any 16 bit I/O cards. There wasn't much business sense to build such, as it would have quite limited possible sales.
(CPU)-Boards according to the IEEE standard for 16 bit access (*1) had to be able to turn any 16 bit request into two consecutive cycles to enable seamless interaction with 8 bit boards. Making a card requiring single cycle 16 bit access would have limited the use to 16 bit CPUs only.
But there have been several memory cards, like this 256 KiB static or this 1 MiB dynamic RAM, that could be configured to for 16 bit transfers using the IEEE 16 bit extension (*1).
In general 16 bit RAM boards are a rather rare find. Usually 16 bit CPU CPUs did bring plenty on-board memory and/or proprietary interfaces (*2), as S100 bus speed was usually limited to 4-6 MHz, considerably slowing down operation.
*1 - See this answer for details.
*2 - Same is true for Multibus boards - but here more to avoid bus arbitrating.