What's considered spam by tumblr?

Got my tumblr deleted although they never tell you that it's suspended untill you email them asking what happened to your account. They said it was considered spam. The account was new and I followed 200 users everyday and posted pictures with watermark on them. I don't post links so what is considered spam? posting pics with watermark is spam? following is spam? what does tumblr think that is considered spam so I can avoid being detected again?

followed 200 users everyday - hitting limit every day = flag + new acc
posted pictures with watermark- 99% sure those pics are not yours = u cannot use watermark
Probably you got also reported by users because it was annoying
Tumblr support sux and they never tell you what you done wrong

Aggressive follow and unfollow method never works with tumblr even you have aged account, You need to make it look natural. Posting water mark pics is not spam.