setuppapersize[A4][A4]
setuplayout[topspace=0.5in, backspace=1in, header=24pt, footer=36pt,
  height=middle, width=middle]

defMPclipFive#1#2#3#4%
  {startreusableMPgraphic{clip:five:#1#2#3#4}{}
     %
     delta  := #4;
     width  := #1-delta;
     height := #2-delta;
     lines  := #3;
     %
     z1 = (0,0);
     z2 = (lines,0);
     z3 = (.5width,height);
     z4 = (width-lines,0);
     z5 = (width,0);
     %
     pickup pencircle
       xscaled delta
       yscaled .5delta
       rotated 30;
     %
     draw z1--z2{dir 135}...z3...{dir -135}z4--z5 withcolor (.5,.5,.5);
     %
     pickup pencircle
       scaled delta;
     %
     draw z1 withcolor red;
     draw z2 withcolor red;
     draw z3 withcolor red;
     draw z4 withcolor red;
     draw z5 withcolor red;
     %
   stopreusableMPgraphic
   reuseMPgraphic{clip:five:#1#2#3#4}{}}

defineoverlay
  [NummerAchtergrond]
  [MPclipFive{overlaywidth}{overlayheight}{30pt}{5pt}]

setuppagenumbering
  [c!location={v!footer,v!middle},
   c!command=NummerCommando]

unexpandeddefNummerCommando#1%
  {framed
     [c!background=NummerAchtergrond,
      c!frame=v!off,
      c!offset=6pt]
     {lower.5dpstrutboxhbox spread 60pt{hss#1hss}}}

%setuppagenumbering[location={footer,center}]

setupbodyfont[11pt,palatino]

setupindenting[medium,yes]

starttext
phantom{Text.}
vfill
midaligned{Text.}
stoptext

documentclass[10pt]{article}

usepackage[T1]{fontenc}
usepackage[utf8]{inputenc}
usepackage[shellescape,tex]{gmp}
usepackage{xcolor}

usepackage{titlesec}

defMPclipOne#1#2#3#4#5{begin{mpost}
      w := #1;  width  := 100;  wfactor := w/width;
      h := #2;  height := 100;  hfactor := h/height;
      color lightred;  lightred  := (.90,.50,.50);
      color lightgray; lightgray := (.95,.95,.95);
      color gray;      gray      := (.50,.50,.50);
      def random_delta (expr d) =
        d-(uniformdeviate 2d)
      enddef;
      z1 = (0,height);
      z2 = (0,0);
      z3 = (width,0);
      z4 = (width,height);
      z5 = (width+random_delta(.2width),height+random_delta(.2height));
      z6 = (.5width+random_delta(.1width),height+random_delta(.1height));
      pickup pencircle
        xscaled (#3/wfactor)
        yscaled (#3/(2*hfactor))
        rotated 30;
      draw z5..z1..z2..z3..z4..z6 withcolor #4;
      pickup pencircle
        xscaled (#3/wfactor)
        yscaled (#3/hfactor);
      draw z1 withcolor #5;
      draw z2 withcolor #5;
      draw z3 withcolor #5;
      draw z4 withcolor #5;
      draw z5 withcolor #5;
      draw z6 withcolor #5;
      newwidth  := (xpart (urcorner currentpicture)) -
                   (xpart (llcorner currentpicture));
      newheight := (ypart (urcorner currentpicture)) -
                   (ypart (llcorner currentpicture));
      currentpicture := currentpicture
       xscaled (w/newwidth) yscaled (h/newheight);
    end{mpost}}

defMPclipFive#1#2#3#4%
  {begin{mpost}
     %
     delta  := #4;
     width  := #1-delta;
     height := #2-delta;
     lines  := #3;
     %
     z1 = (0,0);
     z2 = (lines,0);
     z3 = (.5width,height);
     z4 = (width-lines,0);
     z5 = (width,0);
     %
     pickup pencircle
       xscaled delta
       yscaled .5delta
       rotated 30;
     %
     draw z1--z2{dir 135}...z3...{dir -135}z4--z5 withcolor (.5,.5,.5);
     %
     pickup pencircle
       scaled delta;
     %
     draw z1 withcolor red;
     draw z2 withcolor red;
     draw z3 withcolor red;
     draw z4 withcolor red;
     draw z5 withcolor red;
     %
   end{mpost}}

% I want to combine this with fancyhdr, perhaps, to get the desired result.

newsavebox{tacopage}
newcommand{tacopagenumber}[1]{%
sboxtacopage{#1}%
{ooalign{%
MPclipFive{mpdim{wdtacopage}} % width
{mpdim{httacopage}} % height
{12}
% thickness of the curve
{(.7,.7,.7)}
% color of the curve
{red}
% color of the spots
crhfill
%raisebox{dimexpr.15httacopage+1.5pcrelax}
{boxtacopage}hfill
}}}

% For the section formatting

newsavebox{tacochapterbox}
newcommand{tacochapterhead}[1]{%
sboxtacochapterbox{Largebfseries #1}%
{ooalign{%
MPclipOne{mpdim{wdtacochapterbox+6pc}} % width
{mpdim{httacochapterbox+3pc}} % height
{8}
% thickness of the curve
{(.7,.7,.7)}
% color of the curve
{red}
% color of the spots
crhfillraisebox{dimexpr.5httacochapterbox+1.5pcrelax}
{boxtacochapterbox}hfill}}}

newcommand{secformat}[1]{tacochapterhead{thesection raisebox{-4pt}{textcolor{green}{rule{1pt}{baselineskip}}} #1}}
titleformat{name=section}[block]
{largebfseriesfilcenter}{}{0pt}{secformat}
titleformat{name=section,numberless}[block]
{largebfseriesfilcenter}{}{0pt}{tacochapterhead}

begin{document}


%maketitle
section{A section}

tacopagenumber{a try}

end{document}