זאת תמונה חמודה.

Because תמונה is a feminine singular noun in Hebrew, and the demonstrative זאת means this for feminine singular nouns.

So Hebrew is matching grammatical gender:

• זאת = this (feminine singular)
• זה = this (masculine singular)

Since תמונה is feminine, you say:

• זאת תמונה חמודה not
• זה תמונה חמודה

In Hebrew, the verb to be is usually not expressed in the present tense.

So where English says:

• This is a cute picture

Hebrew simply says:

• זאת תמונה חמודה

This is very normal. Hebrew present-tense sentences often leave out is / am / are.

Because in Hebrew, adjectives usually come after the noun they describe.

So:

• תמונה חמודה = a cute picture

This is the normal Hebrew word order:

• noun + adjective

Compare:

• ילד קטן = a small boy
• מכונית חדשה = a new car
• תמונה חמודה = a cute picture

Because Hebrew adjectives must agree with the noun in gender and number.

Since תמונה is feminine singular, the adjective must also be feminine singular:

• masculine singular: חמוד
• feminine singular: חמודה

So:

• תמונה חמודה = correct
• תמונה חמוד = incorrect

Yes. In modern Hebrew, זו is very commonly used instead of זאת.

So both of these are natural:

• זאת תמונה חמודה
• זו תמונה חמודה

In everyday speech, many speakers prefer זו.
זאת is also completely correct and common.

Here, זאת is functioning more like a demonstrative pronoun: this.

The structure is basically:

• זאת = this
• תמונה חמודה = a cute picture

So the sentence is literally something like:

• This — a cute picture

which in natural English becomes:

• This is a cute picture

If you wanted this picture, where this directly modifies picture, Hebrew more often says:

• התמונה הזאת = this picture

Because the sentence is talking about a cute picture, not the cute picture.

In Hebrew, ה־ is the definite article, like the in English.

So:

• תמונה חמודה = a cute picture
• התמונה החמודה = the cute picture

Your sentence is indefinite, so there is no ה־.

You would normally say:

• זאת התמונה החמודה

Here both the noun and the adjective are definite:

• התמונה = the picture
• החמודה = the cute

In Hebrew, when a noun is definite and has an adjective, the adjective usually becomes definite too.

So:

• התמונה החמודה = the cute picture

A common pronunciation is:

• zot tmu-NA chu-MU-da

More carefully:

• זאת = zot
• תמונה = tmuNA
• חמודה = chamuda / khamuda

A few pronunciation notes:

• תמונה starts with a consonant cluster: tm-
• ח is a throaty sound, often written kh or ch
• the stress is usually:
  • תמוּנָה → tmuNA
  • חמוּדָה → chaMUda

Because this is a very common kind of Hebrew sentence called a nominal sentence or equational sentence.

Hebrew often links two noun phrases directly in the present tense:

• דני תלמיד = Danny is a student
• זאת תמונה חמודה = This is a cute picture

So Hebrew does not need a separate present-tense is in these cases.

The most natural neutral order here is:

• זאת תמונה חמודה

That is the standard way to say This is a cute picture.

Hebrew word order can sometimes change for emphasis, but for a learner, this structure is the safest and most natural one to use.

So as a basic pattern, remember:

• זאת/זה + noun phrase
• זאת תמונה חמודה
• זה ספר מעניין
• זאת שאלה טובה

It is always a feminine noun.

That is a property of the noun itself, not of this sentence only.
Because תמונה is feminine, words that agree with it will also be feminine:

• זאת תמונה
• תמונה חמודה
• תמונה יפה
• תמונה גדולה

So the feminine forms are required whenever grammar calls for agreement.