If you have a rubber that you believe has the best coefficient of friction possible then it wont matter too much how it is shaped unless you need to deal with water or mud like a car tire. The best way to increase the force of friction is to add weight. As you probably know the friction equation is F=uN (F=Friction Force, u=friction coefficient, N=normal force) [Friction force][1]

I don't know what this device does, but if it sees side load and is top heavy it is more likely to tip with a gripy base.

If the issue is that you don't want it to fall over when you set it down... then I'd guess you need this base to help counteract the variation in how level the ground is? In this case, my shot in the dark is three bumps so you just get the minimum three points of contact. Three legged tables don't wobble.   

But if you take nothing else away from this and are simply looking for rubber pattern advice I'd say lighting bolts... Lightning bolts are bad ass. 

  [1]: https://www.school-for-champions.com/science/friction_equation.htm