With a little time and a few supplies, you can make beautiful marbled paper that compares with store-bought.  Here's what you need:

white glossy cardstock

metallic ink refills

water-based ink refills

denatured (rubbing) alcohol

cotton balls

heat tool

spray sealer

Here's how:  Apply small drops of metallic ink (from the refill bottle) onto a sheet of glossy cardstock.  (You might want to work with a 1/4 or 1/2 sheet if you're just making one or two cards.)  Dip a cotton ball into the alcohol, and squeeze most of the liquid out.  Apply small drops of water-based ink onto the wet cotton ball.  Dab the cotton ball up and down all over the cardstock; the inks will blend, creating a marbled appearance.  Swirl the ink to blend the colors and to spread the metallic ink into "veins".  Let the cardstock dry.  To set the ink, dry the cardstock with a heat tool for about 30 seconds.  Stamp with black permanent ink.  You can also use embossing ink and powder.  Spray with a sealer to protect your finished artwork.

Have fun!