No. Various channels are offered as a preview on occasion, but other than subscribing to a large package of channels and downsizing later, there is no way to preview the channel offerings.
As mentioned various channels come and go from free preview. Here is info on how to find out what's currently available:
You can also get a free trial of Amazon Prime:
The other thing that you could consider is switching up your channel subscriptions to preview things for yourself. As an example, if you sign up for 4 theme packs, you can switch these up every 30 days at no cost.