Fish Less Cycle

Decorations, fine. The worst that can happen is that they'll grow a bit of algae especially if the lights are on - it's the ammonia in the water during cycling that encourages algae.

Plants, not too sure. I know that some people do advocate fishless cycling with plants in the tank, as opposed to silent cycling with a lot of plants. Plants use ammonia as food, well ammonium to be precise. The danger is that they might use too much and you won't get enough bacteria, then you get fish, your plants die off if you are as useless with them as me, leaving you with insufficient bacteria for the fish you just got.
Or you could keep the plants in a bucket or other container till after the cycle finishes.

The advantage of putting in your plants now is that by the time your cycle is finished and you are ready to add fish, the plants will already be well rooted and growing. That means your tank will be slightly more "mature" overall. It will also help prevent fish from uprooting plants.
I put in a lot more plants than most people and, while they do grow during the cycle, they are relatively slow until I add fish, from which I conclude that carbon dioxide is the limiting factor during the cycle. Because they are growing quite slowly, I don't think they use all that much of the ammonia. After a cycle, I still have high nitrates, perhaps not as high as they would be without plants, but still needing a major water change before adding fish. This suggests that most of the ammonia is being processed by the filter bacteria. If you only have the small number of plants that most people have, I don't think they would interfere with the cycle much. In any case, the full ammonia cycle should produce enough bacteria, in theory, to allow an almost full load of fish immediately. As very few people stock that heavily all at once, I reckon that if your cycle has completed properly there should be plenty of filter bacteria capacity whether you add plants now or not.