Three key concepts in the research of idioms are discussed: iconography, iconicity, and iconicism. These concepts all have a role to play in phraseology (and beyond), although in quite different ways: Iconography is the mental picture that may be created on the basis of the literal reading of an idiom; it is thus a genuine semiotic concept and not a matter of free associations. However, its functional relevance in discourse should always be questioned. Iconicity in phraseology is the phenomenon that many idioms seem to reflect their semantic content through their form. Although this seems intuitively correct, idiom iconicity is quite relative and always overruled by the arbitrariness of the idiom sign - an arbitrariness which is not relative, but in fact fundamental. Iconicity is therefore often an obstacle to more thorough empirical investigations and cross-linguistic contexts. Iconicism is the tendency found in research and applied contexts that more attention is paid to iconography than to the idioms' rules of use. Iconicism is among other things responsible for textual non-equivalence and non-native style in translations, and it is a "natural", but nevertheless problematic consequence of the iconography and iconicity of idioms.