Crested geckos are not that aggressive and in a cage that size, you may be able to house two males and 5-6 females easily. However, keeping track of eggs may be a problem, if the bottom is filled with coconut husk (bed a beast eco something or other). Eggs lain in cocunum husk will spoil within 36 hours so you will have to check daily for any eggs. Removing this and providing several nesting boxes will make it easier, as you can check the boxes faster.
I beleive day geckos can co-exist with crested geckos, but double check on day gecko requirements to make sure you can maintain temperatures and humidity suitable for both. With the cage so high, you can have warmer areas near the top and the crested geckos will ju st avoid those areas. As day geckos are active during the day and crested geckos mostly at night, there won't be much conflict between the two. Again read up on any species you plan to put together, especially their environmental needs and ability to tolerate others and overall aggressiveness, including towards other species of similar or smaller sizes.
Viviarium type setups are more for advanced herp keepers though, so may be better to pick one species and enjoy them first before adding something new to the mix.
You could also divide up that large cage and put separate kinds of animals that way.
Gargoyle geckos are more aggressive and tend to drop tails alot easier than crested geckos (but unlike crested geckos, they can grow their tails back). Crested geckos can also drop their tails if startled or frightened, but their tails won't grow back. The loss of tail isn't detrimental to the crested gecko at all, most adult crested geckos in the wild are tailless.
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PHLdyPayne