Even so, the Wall of Fire doesn't make attacks.
Wall of Fire is an Attack power. It is an attack, according to the templating used in the PHB.
It doesn't need to -make- attacks. It IS an attack.
It does automatic damage. Since there is no attack roll involved the Wall of Ice takes no damage.
It doesn't need to make an attack roll. It is an Attack power. Thusly, considered an attack by the user. The user is a creature. The creature uses it adjacent to the wall of ice. This can be considered attacking the wall of ice (tho not making an attack, or an attack roll.)
You're not asking about the wall's capabilities here. The creature creating the wall or any and all other conjurations is making any and all attacks involved, and that creature is, in fact, a creature.
So, let's say a spirit conjuration was next to a wall of ice. Spirit powers could be used to attack the wall of ice. 'But conjurations aren't creatures?' Who cares. Irrelevant. The conjuration never made the attack to begin with. It was always the conjurer.
A Flaming Sphere? Conjurer.
A Creeping Doom? Conjurer.
See the pattern?
The presence of an attack roll isn't what makes the conjuration able to affect the Wall of Ice; it is the fact that it is a creature using an attack power.