PWM LED dimmer as TE driver
Yes - you could use a dimme to control a TEC. But do note the following:

With a TEC / Peltier cooler the aim if not using DC drive, is to not introduce significant thermal variations with the driving waveform. If the periods of the lowest frequency components of the driving signal are short compared to the thermal time constants then the TEC will not "notice" changes in thermal input.

If you lowered the PWM frequency such that a control cycle was say 10 seconds long, or if you used an on/off thermostat control (electronic or mechanical that cycled power based on measurable variations of temperature, then you will shorten lifetime. This is due (mostly, probably) to mechanical contraction/expansion cycles "working" the many bonded junctions and their bonding materials). 

Olin has on several occasions made the interesting and seldom made point that if you want operation at less than 100% thermal output then you are better off using filtered DC than PWM. See this answer here for his reasoning.   

RC PWM filter have low efficincy (Efficincy ~+ PWM duty cycle):
Worth noting is that PWM with smoothing using an RC filter is equivalent to using a voltage divider as load with TEC as bottom element and a virtual resistor dropping the supply voltage to the operating point as the upper element. The power dissipated in the virtual resistor is lost - unless you use eg a buck converter or an LC (nominally lossless) filter to reduce the voltage. Note also that an RC filter with PWM will have an efficiency of about the same value as VPeltier / Vsupply = the PWM duty-cycle (eg 30% for 30% on PWM ) and this will apply regardless of filter size. If you use NO formal series R and charge the capacitor with short pulses Murphy will not be fooled - the very large currents that will flow for very short periods when very short pulse and no formal R are used will dissipate just as much energy overall as if a formal larger value resistor had been used.