We have been using a lot of simple square stock in some of our contemporary designs (through our other company - Edmond Kitchen & Bath LLC). Here's some stained knotty alder - square - with a contemporary barn door we recently finished:

Shaker style is very linear. The bow on the Cheyenne doors is not really shaker. These options might be better fits... http://www.homedepot.com/p/compare/?errorURL=ProductAttributeErrorView&langId=-1&storeId=10051&catalogId=10053&prodComp_0=202505917&prodComp_1=202505865&prodComp_2=202505906&prodComp_3=202768990&N=5yc1vZc5ie I know the prices vary a lot, but to stay true to style might be worth it.

Hi Kathy, the doors took such a long time to arrive and were installed only 10 days ago. If you go with the Trustile doors there are some issues to be aware of. The doors are shipped with minimal packaging so it's vital to check for damage (we had some damage). The doors are quite heavy and they come prehung so two people are needed for the installation. The door company sent only one guy so we had to help lift into place. To make sure the warranty stays in effect, the doors must be painted (on all six sides) immediately after installation. I had someone lined up so that wasn't a problem. The Quirk mould is a modern style so if you have any double doors then the door company has to specifically order the square astragal. Our door dealer did not and the old style astragal looks so wrong. I am still in analysis mode for the baseboard and casing. I decided that the 5.5" baseboard looks best and have not made a final decision for the casing. To ensure that the detail of the joined sections between the baseboard and casing is done correctly, the work should be done by a finishing carpenter or a handyman with great attention to detail. Otherwise the 90 degree corners won't look good. The matching casing is 3.5" and little bit thicker so they will not integrate well with the baseboard to be able to join together on the same plane. I plan to order a couple of 12' sections of 4.5" baseboard, have them cut down to 3.5" and then see if looks good or not. That won't be done until the fall, though. I'll post pics once it's done.

They'll be fine if you want to install them on the new doors.