Electrical – My room lights’ brightness pulses when I turn on the toaster oven

More current! What are you using for lighting - arc lamps?

As an animator and photographer myself I'd want to run the lighting as cool as possible. There are some great LED lights out there (or you could build your own). For small stages I've even used LED torches for highlights.

LEDs also have the advantage of running from a regulated DC supply (which gets around your droop problem). You can control intensity (PWM) and color temperature control (LEDs come in all sorts of colors).

Modern digital cameras (video and still) operate quite happily in lower light conditions giving well saturated color.

Just on a Health and Safety point

(1) Drawing a higher current than the wiring was designed to take greatly increases the risk of fire. You really do not want to cause a fire. The fact that your lights dim means that the system is straining to cope with normal demand.

(2) Hot lights can also cause fires. Especially with various artist's materials being used (bits of paper, paint etc.)

The problem isn't within the toaster, and adding a "power conditioner" wouldn't help. It's simply drawing a lot of power from the outlet, and the wiring impedance between the outlet and the distribution panel is causing the voltage at the outlet to drop a bit.

In general, the lighting circuits and the countertop appliance circuits should be on separate breakers to begin with, so that an appliance fault won't leave you in the dark with a potentially dangerous situation (hot and/or spinning objects).

You should try to work out which outlets in your kitchen are on which circuits, and operate the toaster on a separate circuit from the one your lights are plugged into.