For example in these cases "de" and "para" seem to be interchangeable:
muebles de oficina / muebles para oficina
juguetes de niños / juguetes para niños
Are there any other cases where "de" and "para" can be used in the same manner?
According to Wiktionary, "de" has three uses:
In the first two meanings, "para" (which means "for") is incompatible with "de."
Example as possessive:
Example as "from":
Now, in the third case the two can be interchanged loosely, and in most cases, the one that you choose to use is based solely upon convention. That said, there is a distinction between the two that should be noted, and in some cases using one or the other will result in a change of meaning. Considering one of your examples:
Hope this helps :)