Stained glass trees- Stick small pieces of tissue paper into card. Cut out tree shapes (which can be drawn on the back). Hang trees as decorations, or stick them on a picture- e. do a watercolour background before sticking the trees on.
Art Projects for Kids: Snowflake Art Trading Cards. Punched snowflakes glued to painted watercolor paper. Love these - even little kids could do a series of these in diff winter/Christmas themes, and could gift them to mum and dad as gift tags:)