A token tip if you use/like this would make my day.
This is a customisable version of an Ender-3 tool tray. The tray sits in the middle gap area of the Ender-3 machine, and is primarily attached to the underside of the Y-railing. It can be completely pulled out/off. However, there is a version which also has a small attachment to the right-side leg that holds the tray more stably and prevents it from being fully pulled off the machine. Various configuration options such as tray width, depth (in case you have variation on your machine), logo presence, size and position, number of inner segment trays, inbuilt or removable segment dividers and guides, roundness of corners, wall thickness. Anything I could think of, basically.
Edit: 5/July/2018 - new version which makes the vent holes easier to print.
Edit: 11/5/2018 - added (optional) vents to the left side so the motherboard venting is not impeded.