And if your room isn't that humid, I would feel fairly comfortable hanging a gallery wrap in a bathroom. Well ventilated is the key. If you commonly get mold in your bathroom or other room, I'd say avoid hanging paper prints or canvas. And just be aware that this isn't generally recommended. If I were selling you a canvas, I'd advise you of what can happen.
The key is just be aware of how humidity will affect your wall hanging. If you spent $5, you may not care. But if you've spent even over $50, if you're like me, you'd like to enjoy it for quite some time.
That wall that gets doused with direct sunshine
Well let's just say I wouldn't hang anything there. At least not on a long-term basis. If you do have direct sun hitting your wall, consider buying some sheer curtains to soften the light, or blinds where you can direct the light coming in. Direct sun fades and warps prints and canvas (the canvas is wrapped around a wood frame).
High heat areas
Whether it be a space heater, fireplace, or your home gets really really warm (think closed up vacation home where the weather gets up past 90 degrees on the outside, guaranteeing it's 100+ degrees inside), you'll want to be aware exposure over time will not benefit your artwork. Cracking, warping, fading. This is most relevent for paper prints and canvas.
Yes there are solutions! The key is to know the pros and cons of the different ways art is presented. I'm referring to photography in this article, but some of this applies to other artwork, too.
- UV Glass or high quality Acrylic with a higher UV rating for framed prints:
I think everyone is pretty much aware of what these are. You'll pay a little more than plain glass or basic acrylic, but it's worth it if you want to help prevent that fading and yellowing.
- UV protective coating for canvas gallery wraps:
It's ok to ask the person you're buying from if there is a UV coating on the canvas. You can save money by not having it, but that would be the only plus. Personally, I want my customers to have the UV coating on their investment. The coating also helps protect the canvas from scratches, scuffs, and cracking.
- Metal Prints—waterproof, UV resistant, easy to clean:
Metal prints are the safest bet. They won't warp, mold, and can be cleaned easily. They are also UV resistant. For those challenging climates or rooms with drastic temperature/humidity swings, this is the best solution.