How to improve the range of an IR receiver?
The best options to improve IR reception is to actually modify both the receiver and the remote (though the remote is more important to upgrade than the receiver).

Common modifications include replacing the transmitter/receiver element with higher range/power components (this may be at the cost of space), or adding reflectors behind the elements  to better send/capture the IR signal (aluminum foil works as a great DIY reflector for closed spaces.