See this: https://nostrcheck.me/gallery/unicorn ? This is my gallery there. It makes it easier for me to share whatever media I like over nostr not depending on a specific client support, you can just share the links, on nostr and anywhere else.

Regarding the domain, you could accept it as some sort of readable identification for your profile. Lets say someone wants to impersonate your profile. They can't because your npub (and nsec) are unique and yours (keep the last safe). Most of your followers may not pay attention to the long npub though before realizing it is different if impersonated. The nostr (nip05) domain connects your npub with a readable domain that followers can easily read and also associate with your npub. Not necessary but useful especially if you would like to write to specific relay like relay.nostrcheck.me . Some nostr relays identify and deal with spam based on the lack of nip05 profile representation in the spammers profile. Other nostr relays may allow access based only on nip05. It is not ideal but it is helpful. Moreover nostrcheck.me is one of the few that still offers that for free. Most others are not.