[serg aka lain]

Serega, благодарю за желание помочь.
Я тоже нашёл неплохой вариант, адаптировал под свои нужды всем известный код, с текстурными кнопками.
Получилось вроде-бы не плохо.
И самое для меня главное, он должен работать в любой версии Inno

предлагаю взглянуть

Код:

; Inno Setup Compiler 5.3.5 (ansi & unicode)
; = Emulation of switching-off of style XP =
; http://forum.oszone.net/   <serg aka lain>

[Setup]
AppName=My Program
AppVerName=My Program
DefaultDirName={pf}\My Program
LicenseFile=compiler:License.txt
OutputDir=userdocs:My Program.

[code]

const
  RGN_DIFF = 4;
  RADIUS = 1;
  bidBack = 0;
  bidNext = 1;
  bidCancel = 2;
  bidDirBrowse = 3;
  bidGroupBrowse = 4;

function CreateRoundRectRgn(p1, p2, p3, p4, p5, p6: Integer): THandle;
 external 'CreateRoundRectRgn@gdi32 stdcall';
function CombineRgn(p1, p2, p3: THandle; p4: Integer): Integer;
 external 'CombineRgn@gdi32 stdcall';
function SetWindowRgn(hWnd: HWND; hRgn: THandle; bRedraw: Boolean): Integer;
 external 'SetWindowRgn@user32 stdcall';

var
  FormRegion, InnerRegion: tHandle;
  Panel: TPanel;
  ButtonPanel: array [0..4] of TPanel;
  ButtonLabel: array [0..4] of TLabel;

procedure ShapeForm(aForm : TForm; edgeSize : integer);
begin
  FormRegion := CreateRoundRectRgn(0, 0, aForm.width, aForm.height, edgeSize, edgeSize);
  CombineRgn(FormRegion, FormRegion, InnerRegion, RGN_DIFF);
  SetWindowRgn(aForm.Handle, FormRegion, True);
end;

procedure ButtonLabelClick(Sender: TObject);
var
  Button: TButton;
begin
  case TLabel(Sender).Tag of
    bidBack: Button := WizardForm.BackButton;
    bidNext: Button := WizardForm.NextButton;
    bidCancel: Button := WizardForm.CancelButton;
    bidDirBrowse: Button := WizardForm.DirBrowseButton;
    bidGroupBrowse: Button := WizardForm.GroupBrowseButton;
  else
    Exit
  end
  Button.OnClick(Button);
end;

procedure ButtonLabelMouseDown(Sender: TObject; Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
begin
  ButtonPanel[TLabel(Sender).Tag].BorderStyle := bsSingle;
end;

procedure ButtonLabelMouseUp(Sender: TObject; Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
begin
  ButtonPanel[TLabel(Sender).Tag].BorderStyle := bsSizeable;
end;

procedure LabelMouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer);
begin
  ButtonPanel[TLabel(Sender).Tag].BorderStyle := bsSizeable;
end;

procedure LoadButton(AButton: TButton; AButtonIndex: integer);
var
  Labl: TLabel;
begin
  Panel := TPanel.Create(WizardForm);
  Panel.Left := AButton.Left;
  Panel.Top := AButton.Top;
  Panel.Width := AButton.Width;
  Panel.Height := AButton.Height;
  Panel.Tag := AButtonIndex;
  Panel.BorderStyle := bsSizeable;
  Panel.Parent := AButton.Parent;
  ButtonPanel[AButtonIndex] := Panel;

  with TLabel.Create(WizardForm) do
  begin
    Width := Panel.Width;
    Height := Panel.Height;
    AutoSize := False;
    Tag := AButtonIndex;
    OnClick := @ButtonLabelClick;
    OnDblClick := @ButtonLabelClick;
    OnMouseDown := @ButtonLabelMouseDown;
    OnMouseUp := @ButtonLabelMouseUp;
    OnMouseMove := @LabelMouseMove;
    TransParent := True;
    Parent := Panel;
  end;

  Labl := TLabel.Create(WizardForm);
  Labl.Width := Panel.Width - ScaleX(10);
  Labl.Height := Panel.Height - ScaleY(10);
  Labl.Alignment := taCenter;
  Labl.Autosize := False;
  Labl.Font.Color := clBlack;
  Labl.Caption := AButton.Caption;
  Labl.OnClick := @ButtonLabelClick;
  Labl.OnDblClick := @ButtonLabelClick;
  Labl.OnMouseDown := @ButtonLabelMouseDown;
  Labl.OnMouseUp := @ButtonLabelMouseUp;
  Labl.Cursor := crHand;
  Labl.Tag := AButtonIndex;
  Labl.Transparent := True;
  ButtonLabel[AButtonIndex] := Labl;
  Labl.Parent := Panel;
end;

procedure UpdateButton(AButton: TButton;AButtonIndex: integer);
begin
  ButtonLabel[AButtonIndex].Caption := AButton.Caption;
  ButtonPanel[AButtonIndex].Visible := AButton.Visible;
  ButtonLabel[AButtonIndex].Enabled := Abutton.Enabled;
end;

procedure LicenceAcceptedRadioOnClick(Sender: TObject);
begin
  ButtonLabel[bidNext].Enabled := True;
end;

procedure LicenceNotAcceptedRadioOnClick(Sender: TObject);
begin
  ButtonLabel[bidNext].Enabled := False;
end;

procedure InitializeWizard();
begin
  ShapeForm(WizardForm, RADIUS);

  WizardForm.LicenseAcceptedRadio.OnClick := @LicenceAcceptedRadioOnClick;
  WizardForm.LicenseNotAcceptedRadio.OnClick := @LicenceNotAcceptedRadioOnClick;

  LoadButton(WizardForm.BackButton,bidBack);
  LoadButton(WizardForm.NextButton,bidNext);
  LoadButton(WizardForm.CancelButton,bidCancel);
  LoadButton(WizardForm.DirBrowseButton,bidDirBrowse);
  LoadButton(WizardForm.GroupBrowseButton,bidGroupBrowse);
end;

procedure CurPageChanged(CurPageID: Integer);
begin
  UpdateButton(WizardForm.BackButton,bidBack);
  UpdateButton(WizardForm.NextButton,bidNext);
  UpdateButton(WizardForm.CancelButton,bidCancel);

  ButtonLabel[bidBack].Left := ButtonPanel[bidBack].Width div 2 - ButtonLabel[bidBack].Width div 2;
  ButtonLabel[bidBack].Top := ButtonPanel[bidBack].Height div 2 - ButtonLabel[bidBack].Height div 2;
  ButtonLabel[bidNext].Left := ButtonPanel[bidNext].Width div 2 - ButtonLabel[bidNext].Width div 2;
  ButtonLabel[bidNext].Top := ButtonPanel[bidNext].Height div 2 - ButtonLabel[bidNext].Height div 2;
  ButtonLabel[bidCancel].Left := ButtonPanel[bidCancel].Width div 2 - ButtonLabel[bidCancel].Width div 2;
  ButtonLabel[bidCancel].Top := ButtonPanel[bidCancel].Height div 2 - ButtonLabel[bidCancel].Height div 2;
  ButtonLabel[bidDirBrowse].Left := ButtonPanel[bidDirBrowse].Width div 2 - ButtonLabel[bidDirBrowse].Width div 2;
  ButtonLabel[bidDirBrowse].Top := ButtonPanel[bidDirBrowse].Height div 2 - ButtonLabel[bidDirBrowse].Height div 2;
  ButtonLabel[bidGroupBrowse].Left := ButtonPanel[bidGroupBrowse].Width div 2 - ButtonLabel[bidGroupBrowse].Width div 2;
  ButtonLabel[bidGroupBrowse].Top := ButtonPanel[bidGroupBrowse].Height div 2 - ButtonLabel[bidGroupBrowse].Height div 2;
end;