The most important first impression of any content is the image - the old adage of a picture tells the story of a thousand words is true.
This is certainly true when it comes to your LinkedIn profile picture. We had a photographer come in and do ours so I have stuck with mine. Frankly it is probably the best he could have done with the subject he was given! The thing is looking around LinkedIn there are some truly awful ones. Whatever you write and however wrong this fact is your picture does matter - so my advice is get it right.
Yesterday I was at an exhibition next door to a guy from LinkedIn and he reiterated what Joe Burridge from Hudl says below - adding a professional looking photo to your profile makes you 14 times more likely to be found on LinkedIn.
Joe has written a great post here about how he had in the past got it wrong and his advice on getting it right. I completely agree with him.