scenic quartz
While the planet is more or less entirely a desert, there may still be room for different environments, or more specifically different kinds of deserts. And in those deserts we could have different things to live and grow.
Make sure your own suggestions are still thematic to the extremely dry deserts and thin atmosphere of Baltarus. With that said, alien things can still do anything we think they can, creatures, plants and planets included. Stay creative :)
Environments as map ideas:
Black (basalt) sands - Places with past volcanic activity where traditional white and yellowish silica rich sands are replaced by black sands and usual rocks is replaced by porous volcanic rock or pretty columns of basalt.
Volcano - Similar to the one above, but with a still active volcano. Some parts of the map, the lava, could be dealing damage to units that get too close, creating natural barriers even for aliens. Ground is covered by ashes, baltarium patches grow mica crystals instead.
Meteor field - A map with tons of craters where rocks may fall down randomly all over at any moment, damaging structures and units alike. Baltarium is stored in rings around the circumference of the craters (thrown out by the impacts). The small damaging meteors will not deform the terrain to make their own craters.
Rift split - The map is divided by a deep rift between the two halves, making only long ranged and flying units viable.
Salt flats - Just a white plane bound to get a lot of players salty. Balterium here grows large salt crystals instead, which are harder to break, acting as terrain obstacles for anything but harvesters.
Glass crater - The aftermath of the first and the last nuke being used on Baltarus, where humans found the hard way that throwing a massive bomb into a field of baltarium cannot result in anything profitable. The ground here is covered in nuclear glass and baltarium is located only on the edges of the map/crater. Baltarium patches have green silica crystals and glow in the dark, causing negligible but annoying DoT. (radiation for humans is indicated by geiger counter sounds. Aliens will hear whispers or high pitched whizzing sounds instead.)
Environments as Map features:
Boneyard - Likely just a portion of the map with multitude of bones and stones creating a maze of columns and archways providing a lot of cover for vehicles and crawlspace for aliens.
Crystal oasis - A centrepiece of a map where a geyser (or an extreme artesian well) spews up water. The water contains balterium, resulting in heavy growth of crystals around the geyser.
Fertile soil - Patches of fertile soil are scattered across the map. These do not provide biotics until the alien commander builds a structure on top of them. The structure seeds the patch with alien flora. These farms generate a slow trickle of biotics for the shrimps to collect, multiplying the amount of biotics invested into the structure over time. The patch eventually runs out of nutrients and the alternative source of biotics thus runs out.
Algae, mosses, succulents and cushion plants - Another potential source of biotics growing on rocks and cliff faces, it is however far easier to spot by humans and thus they may choose to cut the aliens off from them or use them as bait. If a human manages to reach these plants, they may take a sample in the form of a flower, boosting their personal resources.
Xenobiological fossils - When found by humans, they may be quickly examined for a boost to personal resources or a discount on the next science upgrade.
Long dead coral - Remnants of the planet's once aquatic surface, these giant formations provide limited cover as they can be broken. Like bunkers, but working only as barricades.
shy island
A map in a location with zero shelter from solar radiation, experiencing extreme temperature changes with the rotation of the day/night cycle. Riverbeds carved by liquid mercury split the desert, the mercury boiling and leaving dry trenches before cooling in the atmosphere and falling again as rain at night to refill them. Being out in the open at noon is fatal to infantry.and damages lighter vehicles over time. Cave systems give infantry a place to hide while the sun is intolerable.