List of (almost) all way to change form!

[Metastachydium]

Got it, my bad I mixed them together. I must admit it is hard to differentiate them since they have the exact same name

Yes, they do! Isn't that glorious?

And if you have some more, I would gladly add them to this list.

On it, chief! For now, I give you:
the Half-Rakshasa (LA +3template)^DraMag313 with Disguise Self as a 3/day SLA;
Harssafs^MM3 (6 RHD, LA +4; it has nice stuff, but it's very not worth ECL 10) with Sand Form (Su) that allows them to turn into a pile of sand at-will (mechanically identical to a Gaseous Form spell that doesn't grant flight); and
Forestkith Goblins^MM3 (LA +1) with Tree Shape (Su), as the spell with the same name, technically at-will if I read it right.