I think you have to make these things better:
*Eyecandy
*Terraining
*Balance
*Possibility of moving through the entire map, except for the areas you don't want someone to go to
*Triggers
*Optional:Cinematics
These are helpful links:
http://aom.heavengames.com/scendesign/FAQ
http://aom.heavengames.com/scendesign/basics/BasicTriggers
http://aom.heavengames.com/scendesign/basics/modi
http://aom.heavengames.com/scendesign/basics/cinematics
http://aom.heavengames.com/scendesign/basics/terrain1
http://aom.heavengames.com/scendesign/basics/terrain
http://aom.heavengames.com/scendesign/advanced/transformtriggerguide
http://aom.heavengames.com/scendesign/advanced/Yeebaagooon_Cinematics
http://aom.heavengames.com/scendesign/advanced/invisible
http://aom.heavengames.com/scendesign/advanced/questvar1
http://aom.heavengames.com/scendesign/mapdesign/ovr1
http://aom.heavengames.com/scendesign/mapdesign/ovr2
These are the most helpful to begin, but you can find many others!
Greetings,
WRP_Beater