This code will do it. Without having seen yours, can't say what needs to be changed.
This draws 2 button 400px wide with 3 lines of text each. The background image is a 5x5 pixel + symbol.
The first stretches the image to cover the button. The second simply tiles the image.
<!DOCTYPE html>
<html>
<head>
<style>
button
{
background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHklEQVQIW2NkQID/QCYjiAsmoABFEMRBAThVYmgHAAhoBQWHhfyYAAAAAElFTkSuQmCC);
border-width: 4px;
width: 400px;
}
#btn1
{
background-size: 100% 100%;
background-repeat:no-repeat;
}
</style>
</head>
<body>
<button id='btn1'>This is<br>some text<br>Line 3</button>
<button id='btn2'>This is<br>some text<br>Line 3</button>
</body>
</html>