This is very nice, k-wix, it is full of expressive layers of orchestration. I really like the marching drums. That snare in particular sounds quite good. The instruments are well balanced. Very dark and moody piece, I like it.
The song takes nearly 30 seconds to get going though, I thought my speakers were failing, as I heard almost no sound until about 0:25. The intro needs to come up in volume much quicker. At 0:30 the jump in volume is jarring.
It takes awhile also until I hear the source tune, and when I do, it is played verbatim. Maybe you could change the cadence of the main theme here or there, to add interest? Move some of the notes around, forward or back? Add some 1/8th or 1/16th notes even? The flute or another instrument could play the source melody verbatim in the background while up front, some variation of it is playing.
The song is highly quantized with the notes always hitting right on the beat. Also, most of the instrumentation is lacking in humanization: the strings, the flute, and the brass, all sound very mechanical. It is a tremendous pain to humanize these orchestral parts... but makes all the difference. PM me if you want some tips on doing this. I also use FL Studio.