Visual hallucination or something of that nature always indication of tumor?

No: Visual hallucinations can happen with a number of conditions, not just brain tumors. Delirium of all types is one -- especially alcohol withdrawal delirium and intoxication with hallucinogens. Some medications can cause these especially in older people. Dementia with lewy bodies; migraines; seizures; and creuzfeldt-jakob disease. Also, about half of people with parkinson's disease have these.

Not always : Tumors in certain areas of the brain are known to cause hallucinations, but other things that can cause hallucinations are any one of the psychotic disorders. This means schizophrenia, schizoaffective disorder and some extreme cases of major depression.