Questions regarding voltage divider for micro controller sensing
Your voltage divider circuits seam OK to me. Given that there are no
other requirements, this is a feasible way of measuring these
voltages.
Your question is too unspecific. It is always possible to improve
something. It depends on what your requirements are. With the 10bit
ADC of the Attiny85 you have a theoretical signal to noise ratio of
60.2dB. So this is the best you can do with this ADC converter.
If you want low temperature drift and tight tolerances, you can use C0G/NP0 type SMD parts. I would use a unpolarized cermic cap with much lower capacity (100nF), e.g. this one GRM31C5C1H104JA01L. But I think that also an X7R rated (standard) SMD ceramic capacitor could be OK for your application. For resistor, you could use this one (10K, 1%, 1206 case size): CRG1206F10K. Please be aware that there are a lot of capacitors or resistors that could fit your application.