Any ideas on what the species should look like, then maybe someone who is artistically inclined could do some concept art.
Going by the models shown in the thread, I'd say rather squat and rotund. No neck but with two eyes highly articulated like a chameleon. Give them two main tentacles with the ends split into at least three multi-jointed fingers. They have a caste system where having more than three fingers is a higher caste. Individuals with up to six fingers on both tentacles have been born (hatched?) they're highly intelligent but tend to be quite scatterbrained and for unknown reasons have a much shorter lifespan, though they also mature faster. Unfortunately most of the six fingers are also sterile, especially with both tentacles having six fingers. In their entire recorded history, only three have lived with seven fingers on both tentacles. Those three were prolific inventors and achieved mental maturity astonishingly quickly. The last one invented the FTL drive their species has used to travel to other star systems. It was amazingly NOT sterile and managed to breed three offspring, all of which were boringly normal three fingers who showed no signs of abnormalities and whose descendants have produced nothing but completely normal three fingers.
An uncommon genetic defect causes fewer than three fingers on one or both tentacles, combined with reduced mental ability. An extreme form of the defect causes no fingers at all and extremely low mental ability.
Two more tentacles that are a bit shorter but thicker, stronger and no fingers. The tentacles have dozens of vertebrae-like bones. The're digitigrade (legs like the back ones of a kangaroo, shorter yet stronger) so they don't need seats, just fold their legs up and strap to a back support.
With the four tentacles they're very nasty ground fighters, able to hold large weapons. In their pre-space era they developed gunpowder weapons they could hold steady with their large tentacles while the other two were used for loading and firing. This ability came in very handy when they developed fully automatic firearms, able to one-being weapons that for humanoid species would be crew served.
Walking speed is fairly slow but they have a leaping gait that also uses their large tentacles. Especially agile members of their species learn to use legs and tentacles together to jump straight up, up to 3x their body height. In manipulatory member to tentacle combat, the safest distance from one is either just out of tentacle reach or very far away, though if you taunt one too long it's likely to just low jump at you for a squashing tackle rather than follow the ancient rules of non-powered weapons combat. (They can't throw worth s**t so no worries about getting a knife thrown at you.)
Their unarmed team wrestling matches are a sight to see, with the competitors sproinging around until they land within grabbing reach of each other.
