Okay, basing it off the screenshots for a judgement didn't help me much, but after going in the file I came to an answer (53 blocks tall, this map is). Again, getting better, but there needs to be more done than just world editing a box inside of a box, then making a hole connecting the two boxes with what look like four TNT blocks. The surface and inside look just a bit too bland. Not much is going on around either, maybe more can be done to these? For instance, on the surface it's just a bunch of randomly grown trees. Perhaps you could make a small city on top of the gateway, place end portal blocks (not the frame, but the literal portal blocks) around it. This could give the illusion of transporting between worlds. As for the underside, how about a nether-based "city" in ruins. Perhaps even a fort/base would be a nice touch. More natural hills could help greatly, because as of right now, it looks way too obvious that you used world edit. Next, you only have three timers visible. That's around 8:45 between each timer? Perhaps more timers (or better spacing between the second to last and last) would do better.
No chests located, recommended that no-break/no-drop blocks are blocks like the beacons. I also want to note how there is zero stone in this map. Typically, good survival maps need stone for new players to get basic materials if they're playing for the first time. Since your map has no stone, this would be more suited to classic (in this case, taller would definitely be advised. Taller/deeper since there are only three timers I could find). So as it stands right now, I believe you still have room for improvement. As I said on Abandoned Cobblestone Factory, please use BuildBox for map making. If you don't have builder rank, apply for it when you can. You'll get World Edit access, as I'm told. You can even ask for help from others for real-time advice and better feedback than we can provide.
Editing in: I found five timers and one chest. This chest contains a stack of arrows and bread, a stone sword, a bow, a spruce sapling, a red flower, and bonemeal. It's dis-advisable to have a stack of food/arrows when there's few chests in the map, especially when they're all in the same map. Perhaps eight to sixteen in one chest? Reasonable amounts are fine, but a stack is a bit much.
