I tend to usually work with the same size card, 10.5cm x 15cm.  I just find it easier for envelopes and postage etc., but mostly because that is the size my eye creates in.  I guess that I am mostly attracted to bright colours and simple styles because that is what I seem to create.  Which is odd really because I thought when I first started card making that it would be pastel shades and more traditional 'busy' kind of cards.  This one is fancy wrapping paper, some Kindy Glitz glitter glue and some doodling. =^..^=