Your photo is probably the single most important thing on your LinkedIn page. For most people looking at your details, the photo is the thing that they will look at first and remember last. Their overall impression of you will be determined more by this picture than by anything else on your page. If the picture is too casual, you may not be taken seriously as a professional. If you look too stern, you may come across as unapproachable and hard to work with. Ask the question, does this picture portray the image that I want to project to colleagues and acquaintances? If the picture is of poor quality, what does this convey about your attention to detail or about the sort of person that you are?
LinkedIn photos are displayed in a square format. If you upload a rectangular picture, it will be stretched to fit the square and this usually looks awful. It used to be that the correct photo size was 80×80, but this has been increased to 200×200. Right now, as I write this, I still have an 80×80 photo, but LinkedIn has stretched it to 200×200. It looks fine, but if you still have an old 80×80 photo, you should check how it looks and probably plan to upgrade it sooner rather than later. The minimum size should now be 200×200, but you are allowed to upload a photo as large as 500×500, provided the file size is less than 4MB. Acceptable file formats are JPG, GIF and PNG.
You will almost certainly need to crop your photo to the correct size. There are many tools available to do this including some very good free ones. However, the simplest way is to use the editing tool on the LinkedIn web site after you have uploaded your photo. You should aim to include your head, the top of your shoulders and not much more.
Don’t upload a cartoon rather than a photo; this is no longer against the terms of LinkedIn but it doesn’t look professional.
Having a good photo on your profile makes it easier to relate to you as a person. It makes it easier for someone who has only met you once to remember who you are, and it makes it easier for someone to spot you at an event if they are keen to make contact with you.
You can choose whether your photo is only available to your immediate connections or to your network (connections to the third degree) or public (ie anyone and everyone). If you want people who already know you to make contact, I would recommend making your photo public. One of the most frequent reasons for me not inviting someone to be a connection is my not being sure that I have found the correct person, whereas if they had displayed a photo, I could have been sure.