I should have asked a question or two.
What exactly does "making a DIY generator from appliances" mean? Does it mean you will be provided with a source of appliances and have to MacGyver something out of what you have in front of you, OR does it mean that all you have to do is make a rational argument that the components you used, might be found in something considered an appliance?
If the latter is true, this widens your possibilities a bit, for example using peltiers. TEC is found in some so-called appliances, the cheap mini-fridge or wine coolers, so there is the argument for source and they can generate power from a temperature difference. What you use to produce that difference, would depend on how much power you need to generate.
Done crudely as a quick school project on a limited budget for R&D, it would probably be fairly inefficient, but if using waste heat then there is an argument that the efficiency doesn't matter as much as construction and upkeep cost. I mean if the project is just "make this with nothing but the appliance parts", then it is way out there as unrealistic because reasonably, you will use tools, materials, components, even if just talking about connectors or solder.