Markdown only two basic layout modes: inline & block. Before we think about applying others with an attribute or a shortcode, we need to understand them.

The distinction between those two in Markdown seems simple. Every block is surrounded by at least one blank line. Everything written on the same or the directly following line is inline — except lists and their items. We usually don’t need to think about layout modes and use them intuitively correct. One problematic element is the main reason to recall the distinction:

Inline elements
behave like characters and may be embedded in text. They are placed on the same line as long as there is any horizontal space left — and then the line wraps and so on. They may contain other inline elements — like a piece of code in emphasis for example. Inline elements shouldn’t include block elements, but they always need to be embedded in block elements.
Block elements
always completely fill the available width and may include additional vertical space. Block elements may contain other block elements or inline elements. A common example for the latter is a paragraph block, which fills at least one line, but may include an arbitrary amount of inline elements and text.

The Markdown image element is creating some confusion, because its an inline element. Because many images appear visually as blocks, we falsely tend to infer they should be block elements. But a Markdown image is always inline and embedded in an enclosing block. When its placed stand-alone on a separated line, its not only an image but enclosed in a paragraph block of its own.

To generate a stand-alone image resulting in semantically correct HTML, we need the figure shortcode. And we can easily add CSS-styles to resize or move the resulting figure — even beside the main text column.