Silver's Christmas Celebration was the 24th. I missed it again OTZ
The pixiv tag for this year's Silver's Christmas Celebration is シルバー聖誕祭2011
Last year's is シルバー聖誕祭
I'm really disappointed. The Gold&Ruby Fes had much better quality pictures than this. The first シルバー聖誕祭 had better pictures than this. This year's... pas regardable *facepalm*
Good Silver Fes pictures from the first year (シルバー聖誕祭 tag):
(Johto Trio/OT3 fan comic, highly recommended) http://www.pixiv.net/member_illust.php?mode=manga&illust_id=15391639
(warning, minor Green x Silver) http://www.pixiv.net/member_illust.php?mode=medium&illust_id=7789890
Nota bene: Both Silver's Christmas Celebration and Gold&Ruby Fes are limited to the Pokemon Special (known as Pokemon Adventures in English) universe, not the gameverse. "Silver" gives the PokeSpe character and the Sonic character when used as tag. If you are searching for the game Silver, try "Rival" in phonetics.
I wonder if there are Digimon celebrations? I think it should be the time for one, but I cannot remember which so I don't know what tag to use...