Need Help On Making A Halo Map

Please help I need suggestions and or skins
for a map I am making. It is a Siege/Team Hero Survival game. Any help or tips is welcome. I am a noob map maker and this is the longest I have worked on a map. It is based and The Fall Of Reach, so I'm trying to keep it to the story line. (Meaning no Master Cheif :( , But Spartans are useable.) You can reach me on TFT under this name. Thank you for helping