[MD] Image ratio

[andhie]

The image size should be in ratio. the recommended ratios are 16:9, 3:2, 4:3. the garden fragment items can be taller to support more text (e.g. 4:3 ?) while plant list can be 3:2. https://material.io/design/layout/spacing-methods.html#containers-aspect-ratios

Requires discussion on UI Issue spawned from #47