I see motavia having a colorful flag, with warm colors on it...I'm thinking red-orange. I don't necessarily see it having a sandworm since it's seen as a threat, but perhaps it'd have the basic shape of a motavian head on it? (and the symvol could be yellow or something) They've gotta be a tough race to survive the dry/hot climate and deserts.
Dezolis would probably have a blue flag to represent their cold planet. The picture on it could be a white flame, representing the holy power of the Eclipse torch.
Palma, I envision it having a green flag. Their world was covered in green, and green does represent life, and that sort of thing.
(ironic, the most lively planet gets blown up) 
As for a symbol, I think that a sword is fitting -- it reminds me of Alis, fighting to protect Algo.
As for Rykros... Are we just sticking to the basic three planets? I'll try to come up with something later if it is in.