More than 200 people have been interviewed following the murder of Valerie Graves, who was found with serious head and facial injuries in a ground-floor bedroom at a waterside property in Smugglers Lane, Bosham, near Chichester, West Sussex, on December 30.
Sussex police have also taken more than 100 statements as part of the investigation but feel there may still be witnesses with important information who have not yet come forward.
The 55-year-old artist was beaten to death as she house-sat with her mother, sister and her sister's partner while the owners holidayed abroad over Christmas.
A 22-year-old man was arrested on suspicion of her murder in January but was released on bail.
Police have previously released an image of a hammer which was found nearby and is believed to be the murder weapon.
They also received around 20 calls following a BBC Crimewatch appeal in January.
Detective Superintendent Nick May, from Surrey and Sussex Major Crime Team, said: "This was a savage attack, where a significant level of violence was used.
"We know that a hammer, found nearby in Hoe Lane, was used by the offender and we are seeking the public's help to catch this person before they hurt someone else.
"We particularly appeal to anyone who knows personally, has met professionally, or has a relationship with someone who is violent and who may have used, talked about or threatened violence with a hammer in the past.
"You may have your own concerns or suspicions about this person already, but for your own reasons have not yet come forward.
"Let me reassure you that we can support you whatever your concerns, but this person must be caught."
Mr May also asked for anyone who was in the area of Smuggler's Lane, Hoe Lane or nearby on the afternoon of Sunday December 29 to 10am or Monday December 30 to come forward.
He said: "If you saw anything suspicious or have noticed anyone acting strangely since I urge you to contact us, no matter how incidental you may think your information to be - it could be a vital clue."
Sussex Police is offering the reward of £10,000 for any information that leads to the arrest and conviction of the killer.
Detectives, supported by neighbourhood policing officers, are knocking on the doors of more than 700 homes in the area in their effort to gather any information that can help them in the investigation.
The Major Crime Team is also being advised by the National Crime Agency to provide further offender profiling.
Mr May said they were keeping an open mind as to the motive for Ms Graves' violent death.
Chief Inspector Justin Burtenshaw, district policing commander for Chichester, said: "Some local residents are obviously concerned and we want to do all we can to reassure them.
"I have ensured that extra patrols continue in the area and the neighbourhood policing team is available in Bosham to speak to residents about their concerns.
"In addition to the extra patrols, there will be daily opportunities to speak to a local officer from 11am to 12 outside the Bosham Craft Centre in Bosham Lane and from 7pm to 8pm outside the Co-op store in Delling Lane."
Anyone with information should ring 101 or email email@example.com quoting Operation Ensign, or call Crimestoppers on 0800 555111.