Hi S&K -- I'd be ebaying, antiquing, and shopping with dimentions on hand in search of a pair of something that you love:
http://www.ebay.com/itm/Pair-28-Rare-Carved-Wood-Folk-Altar-Tree-Boquets-/380248655304?pt=Antiques_Decorative_Arts&hash=item58889605c8
If you're on ebay, make sure to use keywords of things that have meaning to you both -- for one person it might be horses, for another it could be Paris...you're sure to find something special and unique.

If money would allow, I would have both niches electrified and place two beautiful pieces of art - either glass or bronze. I have attached samples of what I was thinking.

Go to Jonathan alders website
2 of his white vases would look great

Coat check and ticket booth? hee hee. Seriously good niches for art work. Light is key. There are many beautiful and colorful glass pieces that can be put there.....and glass pieces are very effective lighted, even is just from the top. Solid Sculpture is trickier unless you have light from all sides. You can look at rope lighting that is concealed behind the trim, all the way around the opening. This will light the entire box instead of light from a top spot only. Other alternative is to put adjustable spots in the barrel ceiling and direct at the niches. This assumes you can get the right angles.

Hi Summer,
Because keeping a real plant alive could be a challenge, why not incorporate "life" through a piece of art?
For added interest, I'd recommend layering items.
Candles for accent lighting (if your cubby is not hardwired) and a bowl for keys.
Have fun and make it your own!
Caroline :)

One other thought.....paint the interior of your niches the white shade of your trim. That will help the box seem lighter and create a neutral background for whatever color of object you place in the niches. Liza's pics are a perfect example.

Your home is lovely!

Here a couple of thoughts:

thanks to all! I love love the urn ideas and the art work.

A lighting alternative - (not ideal, electrical is better): you can get a lighted base (battery operated) for glass sculpture. Here is a battery operated example with a dimmer switch. This is really best for a transluscent art piece. This one is $21 from lights for all occassions. A colorfal blown glass vase would work well on a base like this. downside: you will go through batteries; worth using rechargeables.

Hi there! I think that painting the inside of your niches another colour if the simplest fix to make them stand out. A small piece of artwork hung in the middle would be lovely with some smaller, colouful pieces on the shelf to accent the rest of the room. A lovely home indeed!

My personal favorites:

http://www.illuminatedgarden.com/lighted-branches.html?gclid=CLTQgo2zsbUCFQWonQodamsAyA

wow! Lit willow branches! Now, that's a thought. Aja-are these lit by battery? I am perplexed...

Yes!

I adore them.

And what a selection!

Here is the website

http://www.illuminatedgarden.com/

Here are the battery powered LED Lighted Branches

LED Lighted Branches

BUT WAIT, I HAVE A BETTER VENDOR!

THIS IS THE ONE I RECOMMEND:

http://www.bloomsandbranches.com/ProductDetails.asp?ProductCode=BBRIVCNNAT

[BEST PRICES AND SELECTION!]

I really don't like niches! How about covering one of them with a painting and some fresh flowers or books in the other one.

In addition to some of the great ideas above, what about a pretty mirror with a candle in a beautiful vase in front of it?