Just as the well-known “fleur-de-lis” represents a highly stylized lily or iris, I have recently seen a couple of references to a “fleur-de-pensée”, which is said to represent a pansy.

http://lh3.ggpht.com/calladus/SN1RuJXxv_I/AAAAAAAAA6g/oOkNSmmrt5A/UNSET].jpg (link)

http://data6.blog.de/media/760/5025760_ccea30c747_s.jpeg (link)

I do not know if this stylization has worked its way into heraldry, or if it ever will, but given the pansy’s well-established symbolism to the Freethought community – with some bleed over into secularism, Humanism, and especially with the Freedom From Religion Foundation (FFRF) – it may be chosen as a charge someday…

A pansy would, I assume, be an acceptable heraldic charge, if the flower is sufficiently distinctive; but there would of course be the usual artistic license as to just how it would be drawn.  If you wished to ensure that it would always be drawn as shown in your message, I would think that would have to be specified (not sure just how) in the blazon.

Who knows - some future generation might "get religion" and insist on some ( any) different pansy.

Personal viewpoint FWIW, use of an essentially political and controversial symbol as an heraldic charge is problematic.