Okay so THIS, THESEEE are alternate Palkia/Dialga origin formes.
The official ones are just like??? They're something alright. But my least favourite thing about them is how far they stray from what was already established in Giratina's origin form. They're massive, hyperdetailed horse things that look more like Arceus fusion formes than anything. So, I want you to picture a world were Dialga and Palkia's origin formes were released alongside Giratina's back in 2009.
Giratina's origin form is serpentine, possibly snakelike, but ultimately a strange, mysterious creature as opposed to a typical animal. Origin Palkia and Dialga continue this trend, being based on an oyster and a snail respectively.
Most people are confused by Palkia's typing upon seeing its altered forme, but its origin forme makes things clearer. It better resembles an oyster, with its wings and torso extended into a clam shape and a pearl in its center, signifying the center of the universe. Being an oyster is a metaphor for spatiality, as it wraps itself around all that is known. Its fins and neck broaden to resemble the wings of a rocket ship, which is also a nod to the spatial element of this pokemon.
On the other hand, Dialga has elements of the scaly-foot snail (a snail which develops defensive scales over its skin like metal armor). Being a snail is a metaphor for time slowing down and everlasting wisdom. Its back legs are replaced by said scales, albeit more elegant and cape-like. Details on its chest, sail and head resemble a snail shell, with a large diamond placed on each side of its head signifying its intelligence. Its sail, head, top horns and bib make a total of twelve points to match the twelve points of a clock, while its two large front legs point at the edges and resemble the hands of a clock.
Both formes fit right in with Origin Giratina and the three live happily ever after.