I think one basic requirements for a Super Sentai theme is that Japanese children need to think it's cool. Not sure that's true for flowers or emotions.

Let me redeem myself:

Band Theme

Core:

Red - Microphone/Vocals

Blue - Guitar

Yellow - Drums

White - Keytar

Black - Bass

Sixth:

Purple - Pick Up

You could totally do flowers if you pass them off as being part of some samurai imagery and give the kids cool cyber flower collectibles or something.

Emotions could also work very well - Digimon pulled it off.

Another medieval-motif sentai.

i like see dragons sentai or other alien sentai like flashman or other poilce sentai like spd

I like series with fantasy themes over sci-fi themes most of the time, but we've had several shows that are more fantasy than sci-fi in a row. I'd be into it if they went a little cyber-punky for the next Sentai.

Why not one based on the Ocean? We've seen aquatic mecha as support. (Hurricanger, Shurikenger, Ninninger, Goseiger) Why not a team of 3 to start? And the premise is the Villains are after all of Earths resources, but start in the ocean?

An ocean/sea/water based series would certainly be an interesting change of pace. This looks like a job for Aquaman, indeed~

if they used marine life as the ranger motifs, they'd have a HUGE variety of animals to draw from, heh. Would be a surprise to see sharks or whales in consecutive Sentai series, though.

Well, with the sheer amount of sea life, sharks might not need to be used (Though they probably would be, anyway).