I am trying (in solidity) to write a contract that needs some statistics on the past few miners. E.g., who mined the last 100 blocks. I know that for the current block I get the address as explained here. I can also get the last 256 blockhashes, but is it at all possible to get the address of the miners of the last blocks?
No, it's not possible directly within Solidity and the EVM.
As you've noted, these are the only block variables available:
block.blockhash(uint blockNumber) returns (bytes32): hash of the given block - only works for 256 most recent blocks block.coinbase (address): current block miner’s address block.difficulty (uint): current block difficulty block.gaslimit (uint): current block gaslimit block.number (uint): current block number block.timestamp (uint): current block timestamp