I do not by any means have the largest handkerchief collection. (Though I think my Fairy Vintage Godmother does...) I do, however, enjoy collecting them and have ever since high school. I have both modern and vintage - I thought I'd share a few pics of my favorites...
Modern -
some of these actually might better qualify as scarves, but are all square or rectangular and could be both. First off, my absolute fave:

I love the shade of blue plus the beautiful designs on it - it's just perfect.
This one is actually kind of vintage - it was my mum's and I think maybe '70's?? It was big enough to tie up in my hair in a pony tail. Very cute.

This one is good for funerals...

And this one I can't believe I bought at Old Navy years ago. They don't carry too much 'pretty' stuff anymore - more trendy items these days.

This is either Old Navy, or most likely Target. I love the tiny blue flowers.

Vintage -
These are genuine, bonafide hankies and a wide variety...
I love delicate borders like these and white on white embroidery. Subtle and pretty.
This one I found in St. Charles at an Antique shop on Mother's Day. Perfect timing since it has my mom's name on it...

A close up - can you believe the detailing?? I love this one! It's a delicate pink with white embroidery.

I love embroidered flowers...