Hola martini002.
Podés hacerlo de este modo:
Código Delphi
[-]
...
type
TImage=class(ExtCtrls.TImage)
procedure CMMouseEnter(var Msg: TMessage); message CM_MOUSEENTER;
procedure CMMouseLeave(var Msg: TMessage); message CM_MOUSELEAVE;
end;
TForm1 = class(TForm)
Image1: TImage;
private
public
end;
var
Form1: TForm1;
implementation
uses jpeg;
procedure TImage.CMMouseEnter(var Msg: TMessage);
begin
Form1.Image1.Picture.LoadFromFile('C:\Tu_Ruta\Imagen1.jpg'); end;
procedure TImage.CMMouseLeave(var Msg: TMessage);
begin
Form1.Image1.Picture.LoadFromFile('C:\Tu_Ruta\Imagen2.jpg'); end;
...
Saludos.