Old parchment v.2.3 (more realistic with CSS and feturbulence)

parchment.html

<main>
  <div id="parchment"></div>
  <div id="contain">
		<p class="inkTitle">In hoc Signo vinces</p>
    <p id="labarum"><img src="https://upload.wikimedia.org/wikipedia/commons/thumb/2/2c/Chi_Rho.svg/1200px-Chi_Rho.svg.png"></p>
    <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed non risus. Suspendisse lectus tortor, dignissim sit amet, adipiscing nec, ultricies sed, dolor. Cras elementum ultrices diam. Maecenas ligula massa, varius a, semper congue, euismod non, mi. Proin porttitor, orci nec nonummy molestie, enim est eleifend mi, non fermentum diam nisl sit amet erat. Duis semper. Duis arcu massa, scelerisque vitae, consequat in, pretium a, enim. Pellentesque congue. Ut in risus volutpat libero pharetra tempor. Cras vestibulum bibendum augue. Praesent egestas leo in pede. Praesent blandit odio eu enim. Pellentesque sed dui ut augue blandit sodales. Vestibulum ante ipsum primis in faucibus orci luctus et ultrices posuere cubilia Curae; Aliquam nibh. Mauris ac mauris sed pede pellentesque fermentum. Maecenas adipiscing ante non diam sodales hendrerit.</p>
<p>Ut velit mauris, egestas sed, gravida nec, ornare ut, mi. Aenean ut orci vel massa suscipit pulvinar. Nulla sollicitudin. Fusce varius, ligula non tempus aliquam, nunc turpis ullamcorper nibh, in tempus sapien eros vitae ligula. Pellentesque rhoncus nunc et augue. Integer id felis. Curabitur aliquet pellentesque diam. Integer quis metus vitae elit lobortis egestas. Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Morbi vel erat non mauris convallis vehicula. Nulla et sapien. Integer tortor tellus, aliquam faucibus, convallis id, congue eu, quam. Mauris ullamcorper felis vitae erat. Proin feugiat, augue non elementum posuere, metus purus iaculis lectus, et tristique ligula justo vitae magna.</p>
    <!-- This is a red wine cachet ... but shh ! -->
    <p class="cachet"><img src="https://i.postimg.cc/4NBYNqCR/22.png"></p>
    <div id="signature">Imperator Caesar Flavius Constantinus<br />Pius Felix Invictus Augustus</div>
  </div>
</main>

<svg>
  <filter id="wavy2">
    <feTurbulence x="0" y="0" baseFrequency="0.02" numOctaves="5" seed="1" />
    <feDisplacementMap in="SourceGraphic" scale="20" />
  </filter>
</svg>

Parchment.md

Old parchment v.2.3 (more realistic with CSS and feturbulence)

A test to create an "old parchment" effect. Modifications will be create when i will have some time to ameliorate it.

A Pen by Christophe67 on CodePen.

License.

script.js

// First call to define "parchment" height
document.onload = ScrollHeight();

// Redraw when viewport is modified
window.addEventListener('resize', function(event){
  ScrollHeight();
});


function ScrollHeight() {
  var content = document.querySelector('#parchment');
  var container = document.querySelector('#contain');

  // SVG feTurbulence can modify all others elements, for this reason "parchment" is in another <div> and in absolute position.
  // so for a better effect, absolute height is defined by his content.
  content.style.height = container.offsetHeight + 'px';
}

scripts

<script src="https://codepen.io/AgnusDei/pen/bGExVLO.js"></script>

style.css

@import url('https://fonts.googleapis.com/css?family=Pirata+One|Bilbo+Swash+Caps&display=swap');

@font-face {
  font-family: Morris;
  src: url(https://cdn.statically.io/gh/EmmesCodes/Tipografias/dae9f5bb/MorrisInitials.ttf);
  }

:root {
  --fontSize: calc((1vw + 1vh) * .75);
}

*, *:before, *:after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html, body {
	height: 100%;
}

body {
  font: var(--fontSize)/200% 'Bilbo Swash Caps', cursive;
  background-image: url(https://images.unsplash.com/photo-1546484396-fb3fc6f95f98);
  background-size: cover;
}

main {
  postion: relative;
  width: 100%;
  height: auto;
}

/* WARNING ! This solution seems to not work on all navigators.
This problem was reported to me on :
https://stackoverflow.com/questions/14585101/old-paper-background-texture-with-just-css/

August 2021 : ok on Chrome v92+, Firefox v90+, Edge v92+
*/

#parchment {
  position: absolute;
  display: flex;
	width: 75%;
  /* center page with absolute position */
  top: 0%; left: 50%; transform: translate(-50%, 0);
  margin: 2em 0;
	padding: 4em;
	box-shadow: 2px 3px 20px black, 0 0 125px #8f5922 inset;
	background: #fffef0;
  /* v2.1 : borders effect with SVG : try to play with scale to change them */
  filter: url(#wavy2);
  /* v2.2 : Noise added for a vellum paper effect */
  background-image: url(data:image/png;base64,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);
}

/* v2.3 : folds added , remove this part if you don't want them
   I'll try to make it look like crumpled paper if I have time. */
#parchment:after {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: conic-gradient(#fff3, #fff0 2% 24%, #fff2 25%, #4321 0, #0000 27% 48%, #9632 50%, #fff2 0, #fff0 52% 73%, #9632 75%, #fff3 0, #fff0 78% 97%, #9632);
}

main p {
  font-size: 2.25em;
  color: #7F3300;
  margin-top: .75em;
  text-align: justify;
}

div p:not(:first-child)::first-letter {
  float: left;
  font: 1.7em/1em Morris;
  /* a little relief for the first letter*/
  text-shadow: 1px 1px 1px black;
  margin: 0 .5rem;
}

#contain {
  position: relative;
 	display: flex;
  flex-direction: column;
	width: 75%;
  height: auto;
  margin: 0 auto;
	padding: 4em;
}

.inkTitle {
  font-size: 3em;
	font-family: Pirata One, sans-serif;
  text-align: center;
  line-height: 3em;
	color: DimGray;
}

#labarum {
  width: 20%;
  margin-left: calc((100% - 20%) / 2);
  height: auto;
}

.cachet {
  /* image width = 210px and height = 250px */
  /*  5 is one common denominator 210 = 5 * 42 */
  width: calc((100vw * 5) / 42);
  height: auto; /* Height is auto ajusted */
  margin-top: 4rem;
  margin-left: auto;
}

#labarum img, .cachet img {
  object-fit: cover;
  width: 100%;
  height: 100%;
}

#signature {
  text-align: right;
  color: black;
  font-size: 250%;
}