Some places that have nice generic wall art:

• Ruma (https://ruma-home.com/)
• Harvey Norman (https://www.harveynorman.com.my/homeware/art-work/)

Gallaries I've been to that has actual art pieces that may or may not be cheap, but definitely unique:

• Younie Art Gallery (https://www.youniegallery.com/e-gallery)
• Artfordable (https://instagram.com/artfordablegallery?igshid=NjIwNzIyMDk2Mg==)
• Tham Siew Inn (https://thamsiewinn.com/shop/) <- the original works expensive, but got good quality art prints managed by the artist and his family