Are there any other Ethereum clients besides for Geth and Parity which support running a full node?
Harmony is a fully working full node implementation written in java (previously called ethereumj afaik) and cpp-ethereum is a full node implementation written in C++. There are several other implementations in the works. Trinity (previously py-evm, written in python) is "almost done" and is expected to be released soon. There'S at least one other in the works that I can't remember the name of.