Naming and Artwork of graphics in #545 not style guide compliant

[MachtDochNix]

Naming:

• source/external-services/nextcloud/media/SMB02.png

• source/external-services/nextcloud/media/collabora-01.png

• source/external-services/nextcloud/media/index-01.png

• source/external-services/nextcloud/media/index-02.png

• source/external-services/nextcloud/media/install-01.png

Artwork:

• source/external-services/nextcloud/media/index-01.png

• source/external-services/nextcloud/media/index-02.png