You can add or edit your profile picture by clicking your avatar image in the bottom left hand corner and selecting Edit my profile from the drop down menu.
First navigate to Edit My Profile:
Next click on Profile > Then Add Photo:
You can also Replace and Delete your profile pic from here too:
And it's as easy as that! Now you have got your mug plastered all over your teams pages! They won't be able to get enough of the great pic you just uploaded. You could also just use this image of a cat below if you'd like: