When browsing the gallery view (eg http://www.flirtbox.co.uk/dating-online/women_pictures_scotland.html) it's not possible to distinguish straight, bi & gay.

Can I suggest that you change the gender graphic to do two things:
The top image is (in the case above) always the female symbol... it would be male for blokes profiles.
This graphic is imposed on top of another gender graphic (slightly off-set to make it visible): male (for women seeking men); female (for women seeking women), or a double-symbol (for women seeking either/both)