Sylvari Headcanons
(I have)
They can "regrow" their body partially
If they loose a limb,
they can attach the appropriate limp from another (dead) Sylvari and their body and the limb will fuze. (compatibility of other beings has not been tested yet)
they can use any suitable kind of plant though, if the situation calls for it, e.g. a tree branch. But the fusion is very painful as the branch will grow into a functioning limb. Furthermore is this process under high risk to develop more complications in the future and can cause long lasting problems.
the saves method is to take a piece of their own growth pod, as it is genetically fitting. If the Sylvari has been living under different/strange conditions though, for example working underground/in caves, it will be noticable through a different skin tone, as their original color is lighter (different) as it is now.
Tattoos
Tattoos come in form of flowers. Sylvari can put seeds into their skin lappets and flowers will grow. The flowers and the Sylvari have a symbiotic relationship.