OK, /m/booru is obviously a board for 4chan's '/m/ - Mecha' board. As long as it's allowed on /m/, it's allowed here, but we have some other rules too:

+ Porn/hentai/ecchi/whatever is allowed, as long as it's /m/ related. Keep it within the 4chan red board rules though, that means no guro, scat, loli or shota.
+ TAG YOUR POSTS. It makes it impossible for people to find stuff if it's only tagged as 'tagme'. Using the mass uploader is NOT an excuse. Also, be sensible with the tags, don't go putting up like 10 tags that mean the same thing, that's what Aliases are for. Use one tag and suggest the Aliases for it.
+ Don't be a douchebag. Arguing in the comments of a picture, putting up tags like 'not_/m/', deleting tags from pics, and other douchebaggery will get you banned.

Remember to report any posts/comments that break the rules! There aren't enough people to manually trawl though the entire booru looking for things that break the rules, so we need your help! If it's something that there isn't a report button for, use this forum instead.

What about mecha guro like really broken gynoids and stuff?

As long as there's no blood or organs everywhere and it's just mechanical parts, it's fine.

How many size can we upload on server ? I uploaded eva's 2011 calendar(5mb each) and it didn't showed up.

Do you want counter sprites uploading to the regular part? The thread on /m/ 404'd.