I recommend keeping clean separation between personal details and online accounts. Even if this particular thing is a low-medium resolution tracing of a silhouette, because the lines would now be a little blurred, you might forget one day and use it for an account somewhere else that does have personal details on it.
Assuming you mean a profile silhouette, it's not enough information by itself to know who you are, but someone could definitely use it to narrow down details about you. And if someone already has you narrowed down to like 10 possible people, they could definitely use a profile silhouette to single out which one is you.