The suitcases were found hidden behind a wall in Stuttgart’s Schloßgarten by two barbecue-goers on Sunday evening who noticed a trail of blood.
An autopsy on Tuesday found the man, aged 50, and the woman, who has not yet been identified, were killed by stabbing and beating.
Police said the man was known to them and was also well-known among the homeless scene in Stuttgart.
They also believe the suitcases could have been in the park for several days before they were found.
Investigations of the 40-strong police team also show the two victims were killed in a different location before being taken to the park.
The image released shows a metallic blue suitcase with silver horses sprayed on it.