You have time. I finished my level in 3 days and it has more tileset mixing and exanimation than yours. Even though you aren't me or anybody else who can do things that fast, it's still possible to take what you have right now and make a good level out of it. Focus more on level design rather than tileset mixing.
You can definitely make a nice level. Don't follow everyone else's footsteps and make a 10 minute level. Even a simple 2 minute level can score high. Make it fun. Don't overthink gimmicks. Linear doesn't matter as long as it's fun to play.