The latest scorpion version is definitely an upgrade to the first version. Looks much more like a real scorpion and fits nicely into the game. Great! It is also not decorated much like many original non-upgraded units, e.g. hell hounds, pit fiends, rocs, mages and so on.
I also think it totally fits as a lvl 6 unit aesthetically. Would you really think that naga is a lvl 6 unit just based on its appearance (imagine you didn't know the units!)? I don't think so. And same goes for Wyvern and some others.
I guess the only units types discernible by their appearance are lvl 7 and lvl 1, perhaps lvl 2 units. Devil, giant, dragons and so on are taller and a bit more massive than the others and thereby look more powerful.
Because of this, I would definitely downsize the Sand Ghost a good bit, because its size now rather resembles a lvl 7 unit (compare to giant and devil on the one hand and to mage, jinn, efreet etc. on the other hand).
On the other side, I guess cats are a bit to tall for a lvl 1 unit (compared to gremlins, imps, but it's also bigger than golem!). Same for wasps: wouldn't we think that a gargoyle is taller than a wasp? You might compare them to serpent flies to get another impression.
Like Haregar, I finally think that the viper might be slightly too big. To find out, you can easily compare viper to naga and medusa which are similar units aesthetically.
Concerning Lamassu: my feeling is that the color used for wings, beard, etc. is not fitting to the style of the other units. Also for unupgraded version, not many decorations are needed (compare to other unupgraded lvl 7 units). In this respect, to be plain honest, I totally love the version you showed first with all animations on acidcave: Then, the wings and beard had colours fitting way better (darker hair and brownish wings), which is closer to the look of a statue. Also there were less decorations (and normal Behemoth also has no decorations, right? ). You might compare this version to the other Oasis units and also to original game lvl 7 units to see better if I'm right or wrong.