ترجمة - انجليزي-ياباني - Illustration

イラスト is a commonly used word for pictures (drawings.) It is short for the word イラストレーション (from the word "illustration,") though the term may often refer to a piece of artwork in commercial art.

図版 is a word that is referred to when combining artworks, photographs, diagrams and charts, though it is mainly used for printed materials. 画像 (images) is used in a similar sense for contents of web sites.

挿絵 would be a picture accompanying text.