That's a good site joji :)
Have some suggestions based on what grows well around my pond if it helps:
All these take quite moist boggy conditions well -
Caltha palustris (kingcup)
Iris pseudacorus (yellow flag iris)
Juncus effusus f. spiralis (corkscrew rush)
Gunnera manicata (Giant rhubarb - inedible - if you have room)
and plants like Dicentra spectabilis (bleeding heart) and Arum italicum subsp. italicum 'Marmoratum' (lords and ladies) look good near a pond too, as do a lot of ferns.