What lizards have you kept together ?
I will tell you but please don't take my input as endorsement. This can only accomplished with a lot of time, care and responsibility.
I have successfully kept a schneider's skink with a yellow-throated plated lizard for years (and still going strong) in a 40 gallon aquarium. Both are similar in size and are from similar habitat/climate (arid, scrub). They eat the same food. They are both female and very friendly. I doubt I could do this if they were males as they are more aggressive and territorial. In fact my girls often burrow and bask together even though there is ample room to do so separately elsewhere.
Also when I was much younger, I kept a community tank of similar size with a fence lizard (female), 2 house geckos (unsexed), 2 italian wall lizards (male and female) and a five-lined skink (female). It lasted for about 5 years when they started dying off (all were wild-caught adults when acquired - this was the 1980's after all).
I do not recommend keeping different species together unless you really know what you are doing. If you do the research and put the time into seeking a reasonable combination, it can be done. Points to consider in no specific order:
1. Females (especially terrestrial lizards) are usually less aggressive/territorial than males but this may not always be the case as each species is different.
2. If you are not interested in breeding because breeding, egglaying, etc makes lizards less tolerant of each other.
3. Make sure they are the same size so no one becomes lunch. Some lizards may not be overtly aggressive but still cause major stress/intimidation to others in their enclosure just by being larger.
4. You must offer a large enclosure with multiple dens and basking sites. Even lizards that get along need the opportunity for some "alone time" on occasion.
5. Always be careful during feeding time. Even after many years, I am very alert when feeding my lizards despite never seeing aggressive feeding behavior.
6. Arboreal lizards tend to be more solitary and territorial so, in most cases, are completely unsuitable for mixed species enclosures. My grandis females live alone and are extremely happy. I would never wish to change that.
7. The lizards need to come from similar habitat and climate. A rainforest animal and a desert animal have very different temperature and humidity requirements.