Solid work, that looks great! As far as the trays in your canister: Assuming the water enters through the bottom tray and exits at the top tray, you would have media that has fine pores in the middle and the top, like biomedia (biomax, seachem matrix, eheim substrat), Carbon (make sure the carbon is contained somehow in a media bag or something) or fine filter pads (like the white one pictured in your filter above). And some sort prefilter media that is not as sensitive toward the bottom to catch large debris and break it down. Coarse sponges or ceramic prefilter media ('Fluval Prefilter' media is one example of a good prefilter media) are good for the lowest media basket in your filter.