Suggestions, eh?
Using the old adage “Give a man a fish and he can eat for a day,
teach a man to fish and he’ll sit in a boat and drink beer all day”, let me give you what little generalized info I’ve got on Lithops and its relatives.
Lithops and Conophytum are both genera in the family known as “Mesembs”. Mesemb is a shortened version of "Mesembryanthemum". (Scholars are evenly divided as to the original meaning of Mesembryanthemum, some thinking it comes from Old High Elven
Mesii Ammbrian-themu (“Even I Wouldn’t Eat That”) and others saying it’s from the Klingon
M’s’mbr’ank’muk (“That Looks Like My Butt”)). But I digress.
Generally, Mesembs grow in one of two different South African climate zones. The different conditions in these zones cause two very different growing habits and Mesembs can be divided into “summer growers” (actually spring-summer-fall) and “winter-growers” (fall-winter-spring). Lithops are summer growers, so what you need are other summer growers to grow along side of them. Unfortunately (or fortunately, really), there's over a hundred Mesemb genera and it isn’t always obvious when they grow. Also, a lot of the other genera look enough like Lithops that they won’t give you the visual variety you’re probably looking for.
All that said, take a look at
Faucaria,
Frithia and
Stomatium.
But really, what I’ve done is search for “Mesemb” (or “Mesembryanthemum“) in Google “image” mode or gone to the Mesa Gardens listings (no, I’m not getting a commission – more’s the pity), picked a likely genus name and Googled it. Either way, if I saw a plant that I liked, I did some more research and tried to determine the growing season and maybe even some cultivation info… It does get interesting when you get two sources disagreeing on the growing requirements - for instance, I’ve seen
Titanopsis listed as both summer and winter growers.
As I’ve said, I haven’t as yet even finished a full yearly cycle with these plants. I’m far from expert in any of this.
Let me know how you do. Happy hunting.