I am an ex-Realtor so these are all tips I used when trying to sell vacant homes.
If you can't put furniture of any kind (even if it's just a plain chair and side table, lamp) in it then: Put some fresh flowers on the kitchen counters. If that can't be done, second best if fake-anything with color and life in it. Ditto for over the fireplace-maybe some fake plants-ivy, flowers, fall foliage, etc.
Leave a dish out with candies or chocolates in it.
Make sure there are piles of color fliers on the counter for buyers to take home.
A cute homey looking welcome mat by the front door would help too.
Make a binder with all of your manuals, receipts, etc and put them with a color copy of your flyer and MLS listing. Put the MLS listing first, then the color flyer w/lots of photos on it, next the manuals,receipts etc. Place this in an obvious place, like the kitchen counter.
Get a really homey smelling candle like a Yankee or something in a baked good scent and leave the lid off so that the smell permeates the house.
Make sure your realtor has tons of photos online. If you have photos of when your furniture was in it, put them online (unless they are very old) and in your special binder. Also have your realtor make your home a featured listing on Realtor.com if he/she hasn't already done so.
Plant some season appropriate flora outside.
***Very important: Make sure the front door area is very clean and clear. This is extremely important. If your door needs paint, paint it. If the porch is dingy, powerwash it. Etc. The front door and the immediate area inside the door is the first thing buyers see (besides curb appeal) and this has to be a great first impression.
Put a potted season appropriate plant on the front porch (and make sure it's watered by your realtor!)
If your realtor doesn't want to do this stuff, get a new one. I did all of these specific things for my clients. I even took fake foliage/plants, candles, statues, chairs etc from my own house to help stage a vacant house. They should want to sell your house just as much as you do. If you have any more questions you can PM me.