We Will Miss You in Chinese / Japanese...

永遠想念你 is how to write “missing you forever” in Chinese.

The first two characters mean “forever” or “eternally.”
The third and fourth characters mean “missing” or “longing for.”
The last character means “you.”

This might suggest that you are missing someone whom you will never see again (depending on how you read it, or in what context it is used).

一日千秋 is a Japanese and Chinese proverb about missing someone.

一日千秋 is often used to express how hard it is to wait for someone's return or to be away from someone.

Some will translate this as “one day feels like a very long time” or “waiting for someone (something) is hard.”

You might see this romanized as a single word, Ichijitsusenshuu, or as “Ichijitsu Senshuu” from Japanese.
If you break down the characters one-by-one, we get:
一 = one/a
日 = day/sun (can also represent time or date)
千 = 1000/thousand
秋 = autumn/fall

Together, 千秋 can mean “autumn comes thousand times” (or 1000 years). It can also be read as 1000 periods of time.
However, it relays the idea of heartache as you wait for someone you miss.

孤獨 means lonely, solitude, loneliness, and lonesome.
In some contexts, it can mean reclusive, isolated, single, or solo.

孤獨 is a Japanese word but not a good selection for a wall scroll.
In Chinese, this will relay a rather sad feeling to anyone who reads this calligraphy on your wall.

The version shown to the left is the Traditional Chinese and ancient Japanese version. In modern Japan and China they often use a different more simplified version of the second character (as shown to the right). If you want this Japanese/Simplified version, please click on the character shown to the right instead of the button above.