I've grown somewhat skeptical of some of the new-user restrictions, over the years. But the restriction on posting pictures seems to make good sense. Did it really take copious amounts of time to post a picture externally and add a link to it? (Once the link is added, other users can edit the picture directly into your post, which has happened for your question.)
New users cannot answer protected questions. This is the purpose of protection, which should be used sparingly, and sometimes a question can be unprotected to facilitate an answer. Asking for a question to be unprotected, however, is sometimes difficult. Meta would often be an appropriate place for this, but very new users cannot post on meta. Do we really need any restriction on who can post on Meta, besides requiring a registered account? Hmm...
However, the inability to post an answer to a protected question doesn't stop anyone from asking a question or getting help.
New users cannot post as many questions or answers in a very short time as users who have gained a little bit of reputation. I've never heard anyone say this is a problem; I think it goes mostly unnoticed by the vast majority of new users.
Though not in the list, new users typically have to wait some amount of time between posting a question and posting their own answer. If the point of this is to prevent new users from posting things as answers that should be edits or comments... well, that happens a lot anyway and is very efficiently dealt with by flagging. So this restriction seems silly to me. (Maybe it's been lifted, while I was gone?)
