Tumblr lets you add photos to text posts either by uploading an image file from your hard drive or by directly pasting a URL to a picture hosted on a third-party server into the post editor window. If Tumblr fails to properly fetch the linked image, edit the post's HTML code to embed the picture manually.
Go to your Tumblr dashboard and create a new text post by clicking the Text icon.
Compose your text post.
Switch to Tumblr's HTML editor by opening the cog menu and selecting HTML from the Text Editor menu.
Enter the following HTML code at the point where you want to display the image:
Replace the example URL with the correct one.
Publish your post by clicking the Post button.