I'm a newlywed (married in August). Please believe that couples will get enough "junk gifts." Don't get us any special candles or crap we will never use again. No knick-knacks or decor, as you don't know our taste(s).
The perfect wedding gifts are the ones the bride and groom register for. That is what we really want!
Follow their wedding list. Believe me ...you may think the knives and forks are a really dull present to buy...but they are usually really wanted. It is really frustrating to get only half of the cutlery set and find that friends have gone off piste and bought you a flourescent green vase instead!!
Take the wedding invitation to a good frame shop. Have them double-mat it (preferably in a complementary color) and frame it nicely. Silver and gold frames look best. Remember that anything with a mat looks best framed with an extra 1/4" or 1/2" of mat showing at the bottom (meaning, if you have 2" of mat showing at the sides and top, have 2.5" of mat showing at the bottom). This helps the eye visually balance the framed item, as the eye naturally wants to "drag" things downward. This is a useful tip I learned from my art school graduate mother!
It's amazing how many couples look back on their special day and wish they had more pictures. Give the newlyweds a customized gift that they'll cherish forever. Take pictures at their wedding and create a coffee table book with all the candid shots.
Hot glue the wedding invitation (works well for anniversary announcements or birth announcements, too) to a white pillar candle. Dip the candle in parrafin wax (you can get this at a craft store) several times. Send a note to the couple and tell them this is for them to light every year on their anniversary. If the candle burns down too low, they can drop a votive candle down the middle and burn it for many years to come. You can add a piece of trim (lace, pearls, etc.) along the edge of each side of the invitation after hot gluing and before the parrafin dip if you wish. This is a very easy and inexpensive way to give a gift to a couple that they will use and remember you for years to come. :-)
If you know their honeymoon plans and interests, consider treating them to something indulgent during their honeymoon -- a couples massage, a hotair balloon ride, a dinner at a posh resturant, a day of SCUBA diving, tickets to a theatre performance, etc. Have an announcement of the gift (or a gift certificate) sent to their hotel suite with a bottle of bubbly. Helping create wonderful memories can be more meaningful than a vase or a set of towels (no matter how useful)... However, only do this if you know them well -- SCUBA diving for the shark-phobic or ballooning for those afraid of heights would just be a horrible idea.