I would have asked, "How do you imagine God?" or "How do you picture God?" but I was trying to get away from a visual-only picture. I want to ask about His character.
Do you see God as a kind of angry, vengeful deity - like the cartoon Vulcan/Zeus of the "Pastoral Symphony" segment of Fantasia, ready to throw down lightning bolts of doom at the slightest - or no particular - provocation? Just because He can do it?
Do you see Him as the sort of deity who would withhold information from you and then penalize you forever because you didn't know or understand it? Would he require you to do things - or do them a certain way - without telling you about it? Would God obliterate you for offering strange or unauthorized fire without warning you against it first?
- By the way, I don't think that's the case with Nadab and Abihu (Leviticus 10). First of all, they weren't to be the ones handling the incense; that was for their father Aaron (Exodus 30), and before him, Moses (Exodus 40) - and at the altar of incense inside the holy place, in front of the curtain hiding the most holy place. It would seem from v. 4 that Aaron's disobedient sons died outside the tabernacle, in front of the sanctuary - and in full view of the people who had just seen the glory of the Lord.
Secondly, there were commands against using the holy incense for personal use, whenever you wanted to (Exodus 30:37). Later on, King Uzziah's violation of these commands would be punished by leprosy (2 Chronicles 26:16-21).
Thirdly, fire had just come out from the presence of the Lord - I assume that refers to the Shekinah seated on the throne of the covenantal ark in the Most Holy Place of the temple ... would you stand between it and the altar waving censers of holy incense that only your dad was permitted to use? [Some time later, Korah's kinfolk would be obliterated for being presumptuous enough to wave their censers, along with several thousand of their followers. (Numbers 16).]
Fourth, they offered their fire "before the LORD, contrary to his command." (Leviticus 10:1). No mystery there: no example forbidding it, no inference - necessary or otherwise - against it; but a command. Pretty clear. It is right there in the instructions God gave Moses four chapters previously to give to Aaron and his sons that they were not to let the fire of the altar go out, under any circumstances (6:12-13). Think about that for a moment. For what other reason would Nadab and Abihu have brought fire to the altar of sacrifice outside - strange, unauthorized ... or not? Especially after God lit the fire Himself (in the last verse of the previous chapter, 9:24). Do you bring fire to light a fire where a fire's already been lit?
Finally, there's at least a hint that Nadab and Abihu's judgment might have been altered by alcohol, about which God issues an instruction to Aaron while the image of the smouldering remains of those two sons is still fresh in his mind. That instruction would be incongruously cruel if it were not immediately relevant to the situation ... an instruction about something that, like the sacrifice of babies to Him much later in the Old Testament (Jeremiah 7:31), might not have entered God's mind because He thought His children would use better judgment. But it's not like He hadn't given them any instructions. So let's just lay that "Nadab and Abihu" metaphor to rest when describing people who want to worship differently in violation of some possible unexpressed command of God, okay? Aaron's boys should have known better. The rules were in place. It was too important to mess up, especially by partying the night before.) And if the teaching God intended to impart to all generations was "Don't do anything I haven't specifically told you to do - especially in gathered worship," then the logical place for that to be explicitly stated would be verses 8-11. Instead, we read this:
Then the LORD said to Aaron, "You and your sons are not to drink wine or other fermented drink whenever you go into the Tent of Meeting, or you will die. This is a lasting ordinance for the generations to come. You must distinguish between the holy and the common, between the unclean and the clean, and you must teach the Israelites all the decrees the LORD has given them through Moses." ~ Leviticus 10:8-11
It was evidently widely understood that God intended for the entire assembly - not just the priests - to fast from wine (Deuteronomy 29:2-6) while they wandered the entire forty years that God provided water from rocks and manna from heaven (Exodus 16:34-35).
To me, there's a strong likelihood that a whole passel of specific commands of God have been nose-thumbed by the actions of Nadab and Abihu.
So can you really see God judging and eternally condemning people without letting them in on all the rules first? He is sovereign, of course; I'm not saying that He couldn't do whatever He wanted to ... if it were in His nature; His character.
If you still "see" Him exclusively that way, please consider this bit of insight: Psalm 103.