NOTE: This is an example note.

[NOTE]
Alternatively, you can specify the paragraph admonition style explicitly using an AttributeList element.

Renders:

Note
This is an example note.
Note
Alternatively, you can specify the paragraph admonition style explicitly using an AttributeList element.
IMPORTANT: This is another example more important.

Renders:

Important
This is another example more important.
CAUTION: This is another example important but less.

Renders:

Caution
This is another example important but less.
WARNING: This is a warning example.

Renders:

Warning
This is a warning example.
[icon="./images/icons/example.png"]
NOTE: What lovely war.

Renders:

Note
What lovely war.
[TIP]
.A TIP admonition block
=====================================================================
Qui in magna commodo, est labitur dolorum an. Est ne magna primis
adolescens.

. Fusce euismod commodo velit.
. Vivamus fringilla mi eu lacus.
  .. Fusce euismod commodo velit.
  .. Vivamus fringilla mi eu lacus.
. Donec eget arcu bibendum
  nunc consequat lobortis.
=====================================================================

Renders:

Tip
A TIP admonition block

Qui in magna commodo, est labitur dolorum an. Est ne magna primis adolescens.

  1. Fusce euismod commodo velit.
  2. Vivamus fringilla mi eu lacus.
    1. Fusce euismod commodo velit.
    2. Vivamus fringilla mi eu lacus.
  3. Donec eget arcu bibendum nunc consequat lobortis.
Behind the scene

Have a look in the LESS source file less/asciidoc-bootstrap.less, you should have at least this line activated
[https://raw.github.com/llaville/asciidoc-bootstrap-backend/v4/less/asciidoc/admonition-text.less]
:

@import "asciidoc/admonition-text.less";

And this other line deactivated (if you don’t want to use Icons Font feature) :

@import "asciidoc/admonition-iconsfont.less";

If you want to modify the default render, either change the less/asciidoc/admonition-text.less source file, and rebuild the asciidoc-bootstrap.css file, or copy the CSS rules in a new CSS file (free name), and build your page ( AsciiDoc ) with attribute stylesheet.

Important
Your custom stylesheet MUST be located in the {stylesdir}.

E.g:

$ asciidoc.py
  -b bootstrap
  -a linkcss
  -a stylesdir=./stylesheets
  -a scriptsdir=./javascripts
  -a theme=flatly
  -a stylesheet=admonition-text.css
  -a navbar=fixed
  -a totop
  {docfile}
Content of admonition-text.css
.admonition {
    /* bootstrap 3 .alert style */
    padding: 15px;
    margin-bottom: 21px;
    border: 2px solid transparent;
    border-radius: 4px;
}
.note {
    border-color: olive;
}
.tip {
    border-color: blue;
}
.warning {
    border-color: yellow;
}
.caution {
    border-color: fuchsia;
}
.important {
    border-color: red;
}
.note .icon {
    color: olive;
}
.tip .icon {
    color: blue;
}
.warning .icon {
    color: yellow;
}
.caution .icon {
    color: fuchsia;
}
.important .icon {
    color: red;
}
.admonition .icon {
    float: none;
    font-size: 1.33em;
}
.admonition .icon .title {
    margin: 0;
    text-transform: uppercase;
    background-color: #DDD;
    padding-left: 1em;
}
.admonition .content {
    padding-left: 0;
    padding-top: 0.5em;
    margin-left: 0;
    border-left: 0;
    border-top: 0;
    min-height: 0;
}

See results in live with :