There are no deciduous trees that will give you a timber harvest in 20 years, that I know of. You could try hybrid poplar, but there is no market for this material outside of pulp or poultry bedding.
If you are looking to grow high quality timber, then you will need at least 75 years for the rotation. Best species would be site specific. On higher quality sites, you could go with walnut and have yearly nut harvests in about 10-15 years. That gives annual income while waiting for harvestable timber.
I wouldn't discount all the pines. You may be in an area that supports shortleaf pine. These may come to pulp size within your 20 year timeframe. Pines will be able to be planted more dense than hardwoods. Pine pulp is higher valued than hardwood pulp, and would require thinning to enhance growth.
Unfortunately, pine sawtimber is lower in value than hardwoods. However, this is offset by the amount of timber each acre can grow. Pine grows faster, taller, and denser than hardwoods.
Contact your county extension agent. He/she will be able to give you tips, tell you where your state forester is located, and give advice on seedling availability.
