Some more fixes for signs and related stuff. (#50752)

* inhand icons

* Adding to the object, forgot to name one icon.

* Fixing some stuff, and creating inhand icons.

* Fixes a thing I broke.

* Fixes things (including ALL posters) that shouldn't be wrenchable being wrenchable. Plaques now transfer icon_state always.

* Picture frames, painting frames, and the monkey portrait are now wooden.

* Fountain pens can now be uncommonly found in maint.

* Uneditable sign types should not become editable when unwrenched.

* Move redefined var above newly defined var.

code/game/objects/structures/artstuff.dm

@@ -223,7 +223,7 @@
 	name = "painting frame"
 	desc = "The perfect showcase for your favorite deathtrap memories."
 	icon = 'icons/obj/decals.dmi'
-	custom_materials = null
+	custom_materials = list(/datum/material/wood = 2000)
 	flags_1 = 0
 	icon_state = "frame-empty"
 	result_path = /obj/structure/sign/painting
@@ -233,6 +233,7 @@
 	desc = "Art or \"Art\"? You decide."
 	icon = 'icons/obj/decals.dmi'
 	icon_state = "frame-empty"
+	custom_materials = list(/datum/material/wood = 2000)
 	buildable_sign = FALSE
 	var/obj/item/canvas/C
 	var/persistence_id