One of the most important design considerations of a teardrop camper, and something I waited way too long to address personally, is fire safety. In the mainstream RV world, fire safety is governed by standard NFPA 1192. Now, homebuilt campers can violate every conceivable fire safety standard imaginable ... but we can't tackle everything at once!
So the thing I'll throw out there is the concept of a Flame Spread Index, which is basically a measurement of surface burning characteristics. Materials used as interior finishes in RVs, according to NFPA 1192, should have a flame-spread index rating of less than 200.
You can find flame-spread indexes all over the internet. Here's one from the state of Louisiana: http://sfm.dps.louisiana.gov/doc_flamespread.html
Long story short: Most materials are A-okay. What's interesting is that most of the cheap wood-based products, such as OSB, fiberboard, particleboard, MDF, T1-11 siding, cheap sheathing, etc., can creep uncomfortably close to that 200 rating, especially in 1/8-inch and 1/4-inch varieties.
Just something to think about when you're debating the "savings" of building with contractor-grade OSB instead of good plywood
But it doesn't change the science. Some materials are inherently safer (i.e., more flame-retardant) than others, and everyone who has the ability should be building campers to be as safe as possible. You never know when life will change and your beloved homebuilt camper winds up sold - and you don't want to be knowingly selling a matchbox!