Can I send regular attachments but display incoming attachments in place?

With Attachment Tamer's default settings, all attachments are displayed as icons and sent as regular attachments (unless you manually change it using the contextual menu). If you, however, only want to send regular attachments, as opposed to embedded images, but want some or all incoming attachments to be displayed in place, go to the preferences and adjust these settings:

In the Viewing tab, turn off (some of) the Always view as icons options and the Otherwise try to display attachments as they were sent option.
In the Composing and Sending tab, switch Insert attachments to As icons.

Alternatively, If you need to see all image attachments and PDFs displayed in place when composing a message but send them as regular attachments, you can adjust the above settings according to your viewing and composing preferences, and in the Advanced tab, activate the Send regular attachments only option.

If you just need to quickly preview some attachments when composing messages, read this tip.