There are a LARGE number of things you can do to compress your maps file size and optomize said files. I have a whole tutorial that I've left in the graveyard that can explain some things you could do, but to spare you time let me break down some options for you:
(What?) Music and Sound Files:
(Why?) Music can be 4mb for a 4min MP3 track. Even with the quality altered that will only go down to 2MB. This can make it seriously difficult to manage .wav and .mp3 files.
(How?) Delete what you can, if not all of it. It's for the best. If you really have to have one or two files, try to keep them reasonable and low on song time. A good compresser for music and sound files is ImTOO Audio Encoder v2.0. Try using it. There's a tutorial for it in the forums.
http://www.hiveworkshop.com/forums/...ials-278/how-use-custom-music-your-map-31249/
(What?) Change the quality on BLPs:
(Why?) BLPs, when unchecked, can take up massive file size. If done properly, a custom skin can be 30kb, instead of 80-100kb.
(How?) You'll want a File Converter tha tworks on BLPs (Yogbuls) and a BLP Converter that will turn a BMP or TGA into a BLP. (BLP Converter + it's GUI)
First turn the BLP into a BMP, and check to make sure it's not 512x512. If it is, resize it to 50% or 256x256. This will be fine for quality. Whenever converting the file back make sure you change the quality to 25-35% and check the JPEG conversion box.
(What?) Manage your Model size:
(Why?) Models can take up a handful of space, especially the older ones. Some are using animations that you may never use, and some just need a good squishing.
(How?) Grab Oinerwinkles Animation Remover and get rid of those animations you don't use or you think are exorbant. This could shave off 20kb+ from a model depending on the size. If the unit has swim animations, it'll be a good bit of change.
Next is squishing. Grab a squisher like previously mentioned and squish the file once. It won't look different, and the file size will still say it's the same. But place them in your map and close it, and compare it to the old unsquished map and it'll be different.
(What?) Optomizing your map:
(Why?) Optomizing removes a ton of unneccessary data and compresses large quantities of it, as well as speeds up your maps performance and load time over all.
(How?) Grab either pitzermike's Widgetizer, or more preferably, Vexorian's Optomizer. Then check some things, compress, and make sure your map is still playable. If not, tone down the options and try again. This can easily shave off 1/10th of your map size or more.
Hope this has helped you! Good luck.