WordPress.org

How can i adjust the look of the Widget?

Just use the CSS-Class "wGallery" to alter the ul- or li-tags.

How can i get only the images of one/some categories?

Use the category-option include or exclude and enter the id's separated by comma in the options of the widget.

Why doesn't the images link to the parent article?

This option actually only works with "category-option" set to include or exclude.

How do i use the shortcodes?

This is explained here.

Is it possible to show the images at any position in the theme (not only as widget)?

Yes, is explained here

Shortcode-Example using CSS

This is explained here.

For more examples and other questions, take a look at the support forum.