Love is always Open Source and Open Source always is proof of love - hearts as a symbol of love also should remain Open Source
Hearts as a symbol of love always are free to use - but to make sure no other graphic artist ever claims any fake copy rights - just make up your own hearts or modify / beautify hearts to make the hearts of your web site unique and different from other hearts out there.
I have done so for most of the hearts used - they either are created or modified. Some of the very first hearts used on my web site as well as some of the very first flowers used are part of a commercially licensed graphics CD i purchased in my earliest years - hence a very few graphics may have a copyright by the original author.
In general it always is MUCH better to avoid using graphics that already exist out there - be unique in all you do to show that you care and create your own love for others rather than copy and paste for others.
Imagine a woman out there loves your hearts on your web site and one day finds out there are but a copy from another web site created by another man ...
she might fall for the original creator and turn away from you as soon as she realizes that the important symbols or graphic work is made by others.
the hearts "2hearts.gif" is made by someone else on this planet - no idea from where i have it - may be it was part of one of the commercial SW or graphic packages i have ... - thus it is out of my authority to give permission or withhold such as i have no clue about the origin of that file - i only have knowledge about the source of love that inspired mankind to create the symbol of love.
Love and bliss
hans