Yes. You have to, otherwise people wont be able to see your models. I too am creating a big map with lots of models. We have over 12 classes so far and a completely custom terrain. The map is sitting at 26mb, i too have tried to get around it. But sadly enough there isnt a way until blizzard lets us.
I really wouldnt mind, though I use tiny doodads for my map so I would probably have to blow up most of what I have done to scale to the unit's size as I have started experimenting with making use of the 256x256 map and scaling down units to make the entire map look bigger and give me more space to work with.
Also the theme I went with on this bridge was sort of an abstract thing. The absence of builders will let your mind wonder "What happened to them?" as the title is "The Bridge Unscathed" where as it could be still intact and under construction but untouched by the raging war around it =P