Cisco image file names are packed with specific identifiers that signal the underlying platform, feature set, compression style, and software release version. Here is what each segment of vios-adventerprisek9-m.vmdk.spa.156-2.t represents:
The file must be renamed to virtioa.qcow2 (or converted if necessary) for EVE-NG to recognize it. vios-adventerprisek9-m.vmdk.spa.156-2.t