I tend to think of rituals more from the anthropological perspective - as dominant or group symbolism, participation in which secures an individual's status as a legitimate member of a given social group. Baptism is an important ritual in Christianity, as you mentioned, since it affirms one's status not only before God (which might be worth nothing) but before the other believers (which is worth everything). But there are many, many more. As JWs or ex-JWs we're all familiar with the song and prayer combo as a ritual to legitimize religious proceedings: performing the ritual once signifies the commencement of formal religious activity during which our behaviour must conform to certain standards, while performing it again in reverse order signifies that this activity has ended and a different mode of social behaviour now governs our interaction. Service is another ritual activity signifying legitimate participation in the social circle: people who don't go in service regularly are "weak in the truth" (ie undesirable members of the group) while those who regularly participate are held up as models of socially acceptable behaviour. And the JWs regulate sexual behaviour through ritualization by deeming it a sin unless the participants' union is formally acknowledged by God - and, again more importantly, by other members of the congregation, the primary social group.
The social dynamics involved in group interaction essentially force participants to behave in a manner conformist to the standard demanded by the dominant symbolism simply through fear of rejection and alienation by others. To participate is to be safe and secure; to behave differently is to be alone. For our purposes the corollary to all of this, of course, is the WBTS' clever method of forbidding Witnesses from participating in secular or "worldly" rituals that would affirm their legitimate membership in the rest of human society. Witnesses don't participate in birthday rituals, holiday rituals, political rituals, or even "safety valve" type rituals like office parties. This encourages Witnesses to see the congregation as the only social group to which they legitimately belong - hopefully ensuring their continued loyalty to the organization - while simultaneously encouraging them to view other normal human social activity as delegitimized.
So I would actually say that the mirror ritual and the greeting ritual aren't really rituals at all, unless widely adopted by other people as an essential set of behaviours that define legitimate social interaction. I don't know that it's actually possible to create any truly new rituals as they will all take the same essential form: they will confirm some kind of higher governing authority over one's behaviour or perception (irrespective of that authority's true nature) and dictate what is socially proper to do, think, say, etc. I say the hell with ritual: let's all do our own thing.