Hi I'm Pebbles. I am new to this forum and to the Bonsai culture. I have tried to take over care with a bonsai but have had a difficult time of it. As an experiment I started several from seed and have had much better luck. However while purchasing seeds I received some that I found were not what I ordered. I started12 plants of this unknown variety that are the same variety of Maple but I'm not sure what kind they are. Is it possible to make a bonsai out of any variety? If it is, when do I start pinching or do they have to be a certain size? Any help or advise is welcomed.

You are basically asking for a " how to bonsai"... which is impossible.I do hope you dont think that a bonsai will grow out of your seeds, these are normal seeds that will turn into normal trees if left alone.Bonsai are made using a multitude of techniques on specific times of the year, and this for decades.
In short, yes you can make a bonsai out of every tree species, although some species are more suited than others. Most maples are ok. But... a maple is a deciduous tree, which ( assuming you are in the Northern hemisphere) should be dormant now ( as in no leaves). Because you keep yours inside the leaves are still on, your saplings cant go dormant and will die sooner or later. Trees need to be outside, period.

Hard to tell what kind of maple it is with the purple light. Maybe post also a picture with normal lighting.
If it is the normal maple with the big leaves, then you can only make it a real bonsai, if the the trunk is huge. This because of the big leaves and big internotes. I got the advice not to start with those normal maples, but i had them growing from seed last year. But like i was told, the leaves and internotes where way to big on those seedlings, so i composted them all.
Beter spent your time with the right species to get faster results.