Full Idea
The title as given by the artist is something we might need to know (Brueghel's 'Icarus', for example), ...and if a painting depicts one of two twins, it will be the artist's intention that settles which one it is.
Clarification
The Brueghel just shows someone drowning
Gist of Idea
The title of a painting can be vital, and the artist decrees who the portrait represents
Source
Stephen Davies (The Philosophy of Art (2nd ed) [2016], 3.5)
Book Reference
Davies,Stephen: 'The Philosophy of Art (2nd ed)' [Wiley Blackwell 2016], p.67
A Reaction
Those two points strike me as conclusively in favour of the importance of an artist's perceived intentions.