Text World
Visually everything is composed of words and letters in different writing systems. Avatars are simply jumbles of letters, utterances, more sophisticated appearances are maximes, stanzas, limericks and the like. Mating is simply rearranging the snippets.
User avatars vary in transparency, font, style etc. they can move in a variety of ways from fluttering to scuttling and scurrying around.
Plants and landscapes are generated using fractals, L-systems snd the like, instead of pixels, alphabetic characters are used. The text feed may come from any source, on-line, off-line, automatically or user generated. Ideally any place would have objects in different languages.
As an extension to the elementary interaction all viewers can have, an ability to seed new plants by sending messages. Sent text brakes into letters and syllables some of which germinate.
Technically this is a world where objects differ from a virtual garden variety :) world only in that their textures are texts.
However things get interesting when the internet audience is allowed to build structures of texts, hypertext houses and whatnot. Read Moorcock's The Dancers At The End Of Time...
There will be speech kiosks where avatars queue to get themselves spoken, or sent as voice messages to recipients.