@Erik Drentlaw Hi Erik, I have a triplex, and my rental agreement spells out (somewhat vaguely, I think), what tenants can and can't do. I've had tenants who ask for a lot, often in the form of minor improvements. If they ask me to replace a light fixture, because they don't like it, then my answer is they can replace it themselves (with my approval). I tell them that when they move out, if they don't return it to it's original state or equivalent (meaning acceptable to me), then their deposit will be dinged.
I have some tenants who ask for laundry lists of minor things, frequently. I think this is a personality type. They think "It doesn't hurt to ask." I find that if I turn them down on non-essentials, but stay on top of safety issues, they learn that they might be wasting their time. However, I believe I retain their respect, by dealing with safety issues right away.
I think it's fine to let people do minor things to the property, but I think it's important to spell out exactly what your expectations are, and how it might impact their security deposit. I also always think of any potential liability if they injure themselves, which is why I only approve minor changes.
Finally, if you're worried that they might be mad at you, well, I just always try to remember that it's not personal, it's business. Sometimes I have to say this directly to a tenant. I find that if I'm fair and honest, personality issues usually work themselves out. Good luck!
