Do you ever paint?  I used to, quite a bit, but haven't much recently, until a friend encouraged me to try these pretty winter watercolor cards.
I used pan watercolors.  Even basic school grade watercolors work well for this project.  No watercolor paper?  No problem--Royal Sundance Felt cardstock is similar in texture and weight to watercolor paper.

First, some purples.

First, the tree is "painted" with water, which, as you can imagine, is almost impossible to photograph!  In this wet, tree-shaped area, I added little spots of color, allowing it to bleed out as it would.

Adding some magenta . . .

Blue, too!

Green and yellow

Here, the tree shape is painted, but still wet.  You can see that the paint stayed within the water-wet tree shape.  The paint will dry lighter than it appears when wet.

This is what it looks like dry--I like the edge that appears when the wet paint puddles dry.  If you prefer a softer edge, soak up a bit of the wet paint from the edge of the shape with the tip of your dry-ish brush before it dries.

The ornaments were added with a metallic paint

The white snow was spattered on with white watercolor.

There are lots of lovely Stardream Metallic papers--I used a pretty Rose Quartz for the cards, with   Stardream Metallic Aquamarine for the bit of matting, as well as the envelopes.